https://www.nexusmods.com/trialsofmana/mods/117 (Last updated 02 Apr 2021, 最終更新日 2021/04/02)
https://www.nexusmods.com/trialsofmana/mods/118 (Last updated 02 Apr 2021, 最終更新日 2021/04/02)
https://www.nexusmods.com/trialsofmana/mods/191 (Last updated 20 Oct 2020, 最終更新日 2020/10/20)
https://www.nexusmods.com/trialsofmana/mods/206 (Last updated 04 Oct 2020, 最終更新日 2020/10/04)
Recommend using with these MOD.
これらのMODとの併用をお勧めします。

―English Info―
I think there's a big difference between useful and not so useful Ability.
Adjust the effect values of Ability to make them more enjoyable in a variety of combinations.
And, Useful ability have also been adjusted to keep them in balance.
I don't really like to adjust down to fit the weaker one, so it's a basic upper adjustment.

I always play the game in No Future Mode (Do not use the inherited equipment) + Difficulty Rebalanced MOD (Enemy HP*5, Def and MgDef*0.5).
Also, I use cheat to Class Change this way.
Lv1 + At the start of the game : Class 2
Lv18 + Wind Mana Stone : Class 3
Lv38 + Sanctuary Of Mana : Class 4
In the default gameplay, some ability may be too strong.

I've checked the workings, but I was not able to check everything completely.
If you find any problems, please let me know.

The top image summarizes the changes, but it's in Japanese only (MOD work fine in any language).
I didn't summarize the English language because it was hard to look it up, sorry.
I think it won't hurt to use this MOD, so please check using it.

I was able to make this mod with the help of rinnegrid, Thanks rinnegrid!

―Add To―
https://www.nexusmods.com/trialsofmana/mods/256 (Last updated 02 Apr 2021)
After the latest update, the existing difficulty change editor no longer works for bosses (it seems to work for common enemies).
I made a MOD that adjusted No Future Mode more difficultly, so I recommend you to use it together.

―Add To (Ver 1.1)―
Enhanced many of the ability that are triggered by meeting the conditions.
I've also made further adjustments to some of the ability (As before, it's basically an upper adjustment).

-'Attack Help' was changed from 20% to 30%
-'Attack Help II' was changed from 30% to 40%
-'Attack Help III' was changed from 40% to 50%
-'Attacker II' was changed from 40/-40 to 60/-60
-'Reactionary' was changed from 30% to 40%
-'Reactionary II' was changed from 40% to 50%
-'Adversity' was changed from 10% to 20%
-'Defense Help' was changed from 20% to 30%
-'Defense Help II' was changed from 30% to 40%
-'Defense Help III' was changed from 40% to 50%
-'Limit Break' was changed from 5% to 10%
-'Unlimited' was changed from 35% to 50%
-'Bad Luck' was changed from 7% to 15%
-'Bad Luck II' was changed from 10% to 20%
-'Magic Armor III' was changed from 40% to 50%
-'Flourish II' was changed from 40% to 50%
-'Concentrate II' was changed from 40% to 45%
-'Critical Damage II' was changed from 40% to 50%
-'Pinpoint III' was changed from 40% to 45%
-'Love of Mana' was changed from 300% to 400%

―Add To (Ver 1.2)―
Each Boost All is proportionally weaker than each Down All, so we adjusted it to provide the same amount of benefit.

-'Charger' 30% to 150%
-'Charger II' was changed from 75% to 300%
-'Light of Guidance' was changed from 7% to 30%
-'Attack Boost All' was changed from 3% to 6%
-'Attack Boost All II' was changed from 7% to 14%
-'Attack Boost All III' was changed from 10% to 20%
-'Light of Refuge' was changed from 7% to 30%
-'Defense Boost All' was changed from 7% to 10%
-'Defense Boost All II' was changed from 10% to 20%
-'Stat Boost' was changed from 8% to 15%
-'MGC Boost All' was changed from 7% to 10%
-'MGC Boost All II' was changed from 10% to 20%
-'Weak Point All' was changed from 8% to10%
-'Weak Point All II' was changed from 10% to 20%
-'MGC DEF Boost All' was changed from 7% to 10%
-'MGC DEF Boost All II' was changed from 10% to 20%
-'Revive' was changed from 0.5/50% to 0.5/100%
-'Good Luck' was changed from 0.3(30%)/15% to 0.75(75%)/30%
-'Good Luck II' was changed from 0.3(30%)/20% to 0.75(75%)/50%
-'Bad Luck' was changed from 0.3(30%)/7% to 0.75(75%)/15%
-'Bad Luck II' was changed from 0.3(30%)/10% to 0.75(75%)/20%
-'Stat Down Converter' was changed from 20% to 30%
-'Stat Down Converter II' was changed from 25% to 60%
-'Bountiful' was changed from 20% to 50%
-'Love of Mana' was changed from 300% to 500%

―Add To (Ver 1.3)―
In addition to the Normal Ability, I've focused on Class Specific Ability.

―Normal Ability―
-'Adversity' was changed from 10% to 30%
-'Pain Magic' was changed from 20% to 50%
-'Limit BreakIII' was changed from 35% to 45%
-'Blacksmith' was changed from 5% to 20%
-'Stella’s Chain Ability' was changed from 10% to 50%

―Class Specific Ability―
-'Bear It' was changed from 10sec to 20sec
-'Indomitable' was changed from 10sec to 20sec
-'Protective Light' was changed from 10% to 20%
-'Sanctum' was changed from 20% to 30%
-'Mastery' was changed from 15% to 30%
-'Super Healing' was changed from 30% to 50%
-'Magic Burst' was changed from 15% to 30%
-'Refresh' was changed from 15% to 25%
-'Desperation' was changed from 10% to 30%
-'Guardian Runes' was changed from 30% to 50%
-'Soul Hunt' was changed from 20% to 50%
-'Greed' was changed from 3% to 5%
-'Mutiny' was changed from 15% to 30%
-'Fighting Spirit' was changed from 4% to 20%
-'Royal Anger' was changed from 10% to 30%
-'Gem' was changed from 20% to 50%
-'Mercy' was changed from 10% to 20%
-'Distress' was changed from 10% to 20%
-'Security' was changed from 10% to 20%
-'Repetition' was changed from 5% to 10%
-'Life Swipe' was changed from 15% to 30%
-'Item Master' was changed from 10% to 20%
-'Focus' was changed from 10% to 20%
-'Plunder' was changed from 20% to 40%
-'Life And Death' was changed from 10% to 25%
-'Army of One' was changed from 1% to 2%
-'Ward Runes' was changed from 40% to 60%
-'Meteor Light (Before MOD : Mana Blessing)' was changed from 7% to 10%
-'Persistent Effect (Before MOD : Winded Protection)' was changed from 20% to 40%
-'Light Of Relief' was changed from 10% to 20%
-'Surprise Aid' was changed from 35% to 50%

―Add To (Ver 1.4)―
I have created a MOD (see above) that changes the effect of the buff/debuff, readjusted the 'Good Luck'
This will give you almost the same benefit as the debuff.
I also tweaked other Ability in change to that.

-'Wound' was changed from 30% to 60%
-'Wound II' was changed from 40% to 90%
-'Tough' was changed from 20% to 25%
-'Tough II' was changed from 30% to 40%
-'Judge' was changed from 20% to 25%
-'Judge II' was changed from 30% to 40%
-'Cheat' was changed from 20% to 25%
-'Cheat II' was changed from 30% to 40%
-'Wound Magic All II' was changed from 40% to 60%
-'Mute' was changed from 0.3(30%) to 0.4(40%)
-'Doze' was changed from 0.3(30%) to 0.4(40%)
-'Charred' was changed from 0.45(45%) to 0.55(55%)
-'Stonework' was changed from 0.1(10%) to 0.2(20%)
-'Toxic' was changed from 0.3(30%) to 0.4(40%)
-'Toxic II' was changed from 0.3(30%) to 0.4(40%)
-'Toxic Trap' was changed from 0.3(30%) to 0.5(50%)
-'Meditation' was changed from 5sec/7% to 5sec/30%
-'Good Luck' was changed from 0.3(30%)/15% to 0.75(75%)/25%
-'Good Luck II' was changed from 0.3(30%)/20% to 0.75(75%)/45%

―Add To (Ver 2.0)―
Ver. 1.1.0 is supported.
Also readjusted some ability accordingly.

―Normal Ability―
-'Attack Help' was changed from 20% to 25%
-'Attack Help II' was changed from 30% to 50%
-'Attack Help III' was changed from 40% to 75%
-'Reactionary' was changed from 30% to 50%
-'Reactionary II' was changed from 40% to 75%
-'Adversity' was changed from 10% to 40%
-'1-Hit Class Strike' was changed from 25% to 40%
-'1-Hit Class Strike II' was changed from 35% to 60%
-'Mighty' was changed from 5% to 10%
-'Mighty II' was changed from 20% to 30%
-'Mighty III' was changed from 30% to 50%
-'Sturdy' was changed from 80%/5% to 75%/5%
-'Sturdy II' was changed from 80%/10% to 75%/20%
-'Sturdy III' was changed from 80%/30% to 75%/40%
-'Reclaim' was changed from 1 to 2-
-'Reclaim II' was changed from 2 to 4
-'Von Boyage's Chain Ability' was changed from 5 to 20%
-'Ludgar's Chain Ability' was changed from 10% to 20%
-'Counter II' was changed from 30sec/15% to 30sec/20%
-'Attack Saber II' was changed from 25% to 30%
-'Super Trap' was changed from 25% to 40%
-'Super Ninja Trick' was changed from 25% to 40%
-'Defense Help' was changed from 20% to 25%
-'Defense Help II' was changed from 30% to 50%
-'Defense Help III' was changed from 40% to 75%
-'Spell Guard III' was changed from 40% to 50%
-'Cast Resist II' was changed from 30% to 35%
-'Cast Resist III' was changed from 40% to 50%
-'Cherish' was changed from 10% to 20%
-'Recover Break' was changed from 30% to 40%
-'Aurora Sisters' Chain Ability' was changed from 5% to 20%
-'Stat Boost' was changed from 8% to 20%
-'Unlimited' was changed from 35% to 75%
-'Fortitude II' was changed from 20% to 30%
-'Fortitude III' was changed from 30% to 50%
-'Fortitude IV' was changed from 40% to 75%
-'Toxic II' was changed from 0.3(30%) to 0.75(75%)
-'Weak Point II' was changed from 25% to 30%
-'Weak Point III' was changed from 35% to 50%
-'Fraction' was changed from 150% to 200%
-'Special Effect II' was changed from 40% to 50%
-'Special Effect III' was changed from 60% to 75%
-'Victory MP Boost' was changed from 2 to 3
-'Victory MP Boost II' was changed from 3 to 5
-'Effect Boost All' was changed from 30% to 50%

―Class Specific Ability―
-'Sanctum' was changed from 20% to 40%
-'Super Healing' was changed from 30% to 60%
-'Desperation' was changed from 40% to 50%

―Add To (Ver 2.1)―
-'Attacker II' fixed value from 60/-70 to 60/-60
-'Guard Saber' was changed from 15% to 30%
-'Guard Saber II' was changed from 25% to 50%

―Add To (Ver 2.2)―
-'1-Hit CS Boost' was changed from 30% to 75%

―Add To (Ver 2.3)―
―Normal Ability―
-"Attacker" was changed from +30/-30 to +40/-40
-"Attacker II" was changed from +40/-40 to +80/-80
-"Super Summon" was changed from 30% to 40%
-"Victory MP Boost" was changed from 2 to 8
-"Victory MP Boost II" was changed from 3 to 15

―Class Specific Ability―
-"Guardian Runes" changed the effect from "Status effect resistance increase by 30%" to "All stat decreases canceled out"
-"Gem" changed the effect from "Cannot be knocked back while using a charge attack, opponent’s damage decreased by 20%" to "Each time 10% of HP in Damage is accumulated, attack increases by 5% (up to 30%)"
-"Evil Spirit" was changed from 3% to 5%
-"Cutthroat" changed the effect from "10% chance of destroying enemy instantly when attacking enemy with status effect" to "Chance of critical hit increased by 90% when attacking a status affected enemy"

―How To Use―
put in 'Trials of Mana/Content/Paks/~mods'

―説明― 
アビリティは様々存在していますが、有用なアビリティとあまり役に立たないアビリティの差がかなり大きいように感じます。
一部のアビリティの効果を調整し、今まで使いにくかったアビリティを使いやすくなるようにしてみました。
また、有用なアビリティもバランスを崩さない程度に調整を加えてあります。
弱い方に合わせるようなダウン調整はあまり好きでは無いので、基本アッパー調整になっています。

私は常に、ノーフューチャーモード(引き継いだ装備は使わない)+難易度調整MOD(敵HP5倍、敵防御力と魔法防御力0.5倍)、という状態でゲームをプレイしています。
また、私はチートを使用し以下のようにクラスチェンジを行なっています。
Lv1 + ゲームスタート時 : クラス2
Lv18 + 風のマナストーン : クラス3
Lv38 + マナの聖域 : クラス4
デフォルトの難易度でこのMODを導入すると、一部のアビリティが強すぎるように感じるかもしれません。

トップ画像が変更したものの一覧表です。
動作確認はある程度していますが、全てを完全にチェック出来た訳ではありません。
もし不具合を見つけたら遠慮なくお伝えください。

このMODはrinnegridさんの様々な協力により作成することが出来ました、rinnegridさんありがとうございました!

―追記―
https://www.nexusmods.com/trialsofmana/mods/256 (最終更新日 2021/04/22)
最新のアップデート後、既存の難易度変更エディタはボスに機能しなくなりました(雑魚敵には機能しているようです)。
ノーフューチャーモードをより難しく調整したMODを作ったので、こちらと併用するのをお勧めします。

―追記 (Ver 1.1)―
条件を満たすことで発動するアビリティの多くを強化しました。
また、一部のアビリティに更なる調整を行いました(以前同様、基本的にアッパー調整です)。

-「ピンチアタック」を20%から30%へ変更
-「ピンチアタックII」を30%から40%へ変更
-「ピンチアタックIII」を40%から50%へ変更
-「アタッカーII」を40/-40から60/-60へ変更
-「火事場の馬鹿力」を15%から25%へ変更
-「逆襲」を30%から40%へ変更
-「逆襲II」を40%から50%へ変更
-「逆境」を10%から20%へ変更
-「ピンチディフェンス」を20%から30%へ変更
-「ピンチディフェンスII」を30%から40%へ変更
-「ピンチディフェンスIII」を40%から50%へ変更
-「リミットブレイク」を5%から10%へ変更
-「アンリミテッド」を35%から50%へ変更
-「ラッキーダウン」を7%から15%へ変更
-「ラッキーダウンII」を10%から20%へ変更
-「マジックアーマーIII」を40%から50%へ変更
-「一閃II」を40%から50%へ変更
-「集中II」を40%から45%へ変更
-「クリティカルダメージII」を40%から50%へ変更
-「クリティカルアップIII」を40%から45%へ変更
-「マナの愛」を300%から400%へ変更

―追記 (Ver 1.2)―
アップオール系はダウンオール系と比べて比率的に弱いので、同じくらいの恩恵になるよう調整しました。

-「チャージアップ」を30%から150%へ変更
-「チャージアップII」を75%から300%へ変更
-「導きの光を7%」から30%へ変更
-「攻撃アップオール」を3%から6%へ変更
-「攻撃アップオールII」を7%から14%へ変更
-「攻撃アップオールIII」を10%から20%へ変更
-「守りの光」を7%から30%へ変更
-「防御アップオール」を7%から10%へ変更
-「防御アップオールII」を10%から20%へ変更
-「アップ強化」を8%から15%へ変更
-「魔攻アップオール」を7%から10%へ変更
-「魔攻アップオールII」を10%から20%へ変更
-「弱点特効オール」を8%から10%へ変更
-「弱点特効オールII」を12%から20%へ変更
-「魔防アップオール」を7%から10%へ変更
-「魔防アップオールII」を10%から20%へ変更
-「リバイバル」を0.5/50%から0.5/100%へ変更
-「ラッキーアップ」を0.3(30%)/15%から0.75(75%)/30%へ変更
-「ラッキーアップII」を0.3(30%)/20%から0.75(75%)/50%へ変更
-「ラッキーダウン」を0.3(30%)/7%から0.75(75%)/15%へ変更
-「ラッキーダウンII」を0.3(30%)/10%から0.75(75%)/20%へ変更
-「ダウンコンバート」を20%から30%へ変更
-「ダウンコンバートII」を25%から60%へ変更
-「アイテムアップ」を20%から50%へ変更
-「マナの愛」を300%から500%へ変更

―追記 (Ver 1.3)―
今回は通常のアビリティに加え、比較的存在感の薄いものが多いクラス固有のアビリティを中心に調整しました。

―通常アビリティ―
-「逆境」を10%から30%へ変更
-「ペインマジック」を20%から50%へ変更
-「リミットブレイクIII」を35%から45%へ変更
-「ブラックスミス」を5%から20%へ変更
-「生活の知恵」を20%から50%へ変更

―クラス固有アビリティ―
-「やせ我慢」を10秒から20秒へ変更
-「闘志」を10秒から20秒へ変更
-「光の加護」を10%から20%へ変更
-「聖域」を20%から30%へ変更
-「剣聖」を15%から30%へ変更
-「超回復」を30%から50%へ変更
-「マジックバースト」を15%から30%へ変更
-「リフレッシュ」を15%から25%へ変更
-「デスパレート」を10%から30%へ変更
-「加護のルーン」を30%から50%へ変更
-「ソウルハント」を20%から50%へ変更
-「グリード」を3%から5%へ変更
-「反逆」を15%から30%へ変更
-「闘気」を4%から20%へ変更
-「逆鱗」を10%から30%へ変更
-「金剛」を20%から50%へ変更
-「マーシー」を10%から20%へ変更
-「ディストレス」を10%から30%へ変更
-「プロテクション」を10%から20%へ変更
-「サモンパーティ」を5%から10%へ変更
-「ライフリーピング」を15%から30%へ変更
-「アイテムマスター」を10%から20%へ変更
-「集気法」を10%から20%へ変更
-「スナッチャー」を20%から40%へ変更
-「活殺自在」を10%から25%へ変更
-「エインヘルヤル」を1%から2%へ変更
-「守りのルーン」を40%から60%へ変更
-「流星の光 (変更前は女神の祝福)」を7%から10%へ変更
-「魔狼の災禍 (変更前は覇竜の加護)」を20%から40%へ変更
-「救済の光」を10%から20%へ変更
-「神鳥の飛翔」を35%から50%へ変更

―追記 (Ver 1.4)―
バフ・デバフの上昇効果を変更するMOD(上記参照)を作成したため、ラッキーアップを微調整しました。
これでデバフとほぼ同じ恩恵が得られるようになります。
また、それに加えて他のアビリティも微調整しました。

-「ペインアタック」を30%から60%へ変更
-「ペインアタックII」を40%から90%へ変更
-「強者」を20%から25%へ変更
-「強者II」を30%から40%へ変更
-「裁定者」を20%から25%へ変更
-「裁定者II」を30%から40%へ変更
-「アンフェア」を20%から25%へ変更
-「アンフェアII」を30%から40%へ変更
-「ペインマジックオールII」を40%から60%へ変更
-「サイレンス」を0.3(30%)から0.4(40%)へ変更
-「スリープ」を0.3(30%)から0.4(40%)へ変更
-「チャード」を0.45(45%)から0.55(55%)へ変更
-「ストーン」を0.1(10%)から0.2(20%)へ変更
-「ポイズン」を0.3(30%)から0.4(40%)へ変更
-「ポイズンII」を0.3(30%)から0.4(40%)へ変更
-「猛毒トラップ」を0.3(30%)から0.5(50%)へ変更
-「瞑想」を5秒/7%から5秒/30%へ変更
-「ラッキーアップ」を0.3(30%)/15%から0.75(75%)/25%へ変更
-「ラッキーアップII」を0.3(30%)/20%から0.75(75%)/45%へ変更

―追記 (Ver 2.0)―
Ver.1.1.0に対応しました。
また、それに伴いいくつかのアビリティを再調整しました。

―通常アビリティ―
-「ピンチアタック」を20%から25%へ変更
-「ピンチアタックII」を30%から50%へ変更
-「ピンチアタックIII」を40%から75%へ変更
-「逆襲」を30%から50%へ変更
-「逆襲II」を40%から75%へ変更
-「逆境」を10%から40%へ変更
-「一撃必殺」を25%から40%へ変更
-「一撃必殺II」を35%から60%へ変更
-「パワフル」を5%から10%へ変更
-「パワフルII」を20%から30%へ変更
-「パワフルIII」を30%から50%へ変更
-「強気」を80%/5%から75%/5%へ変更
-「強気II」を80%/10%から75%/20%へ変更
-「強気III」を80%/30%から75%/40%へ変更
-「アブソーブ」を1から2へ変更
-「アブソーブII」を2から4へ変更
-「闘魂」を5%から20%へ変更
-「獣の咆哮」を10%から20%へ変更
-「反撃II」を30秒/15%から30秒/20%へ変更
-「アタックセイバーII」を25%から30%へ変更
-「強化トラップ」を25%から40%へ変更
-「強化忍術」を25%から40%へ変更
-「ピンチディフェンス」を20%から25%へ変更
-「ピンチディフェンスII」を30%から50%へ変更
-「ピンチディフェンスIII」を40%から75%へ変更
-「スペルガードIII」を40%から50%へ変更
-「スペルフィールドII」を30%から35%へ変更
-「スペルフィールドIII」を40%から50%へ変更
-「セイントベール」を10%から20%へ変更
-「回復限界突破」を30%から40%へ変更
-「マジックシフト」を5%から20%へ変更
-「アップ強化」を8%から20%へ変更
-「アンリミテッド」を35%から75%へ変更
-「不屈II」を20%から30%へ変更
-「不屈III」を30%から50%へ変更
-「不屈IV」を40%から75%へ変更
-「猛毒トラップ」を0.3(30%)から0.75(75%)へ変更
-「弱点特効II」を25%から30%へ変更
-「弱点特効III」を35%から50%へ変更
-「半減特効」を150%から200%へ変更
-「状態異常特効II」を40%から50%へ変更
-「状態異常特効III」を60%から75%へ変更
-「撃破MP+」を2から3へ変更
-「撃破MP+II」を3から5へ変更
-「状態異常アップオール」を30%から50%へ変更

―クラス固有アビリティ―
-「聖域」を20%から40%へ変更
-「超回復」を30%から60%へ変更
-「デスパレート」を40%から50%へ変更

―追記 (Ver 2.1)―
-「アタッカーII」の数値が60/-70になっていたのを60/-60に修正
-「ガードセイバー」を15%から30%へ変更
-「ガードセイバーII」を25%から50%へ変更

―追記 (Ver 2.2)―
-「一撃撃破SP+」を30%から75%へ変更

―追記 (Ver 2.3)―
―通常アビリティ―
-「アタッカー」を+30/-30から+40/-40へ変更
-「アタッカーII」を+40/-40から+80/-80へ変更
-「強化召喚」を30%から40%に変更
-「撃破MP+」を2から8に変更
-「撃破MP+II」を3から15に変更

―クラス固有アビリティ―
-「加護のルーン」の効果を「状態異常耐性を30%アップ」から「全てのステータスダウン効果を無効化」に変更
-「金剛」の効果を「タメ攻撃チャージ中、仰け反らなくなり、被ダメージを20%ダウン」から「HP10%分の被ダメージ蓄積毎に、攻撃力・防御力を5%アップ
最大30%)」に変更
-「羅刹」を3%から5%に変更
-「ローレスキリング」の効果を「状態異常の敵攻撃時、10%の確率で即死させる」から「状態異常の敵への攻撃時、クリティカル発生確率を90%アップ」に変

―使用手順―
Trials of Mana\Trials of Mana\Content\Paks
のフォルダ内に「~(←半角です)mod」フォルダを作成し、
ダウンロード後に解凍した.pakファイルを移動すれば適用されます。

―日本の方へ―
https://discord.gg/UQS8w8u
まだ日本ではMOD作成が一般的では無く、情報共有の場が無いように感じます。
海外のMOD作者さんが多くいるDiscordに日本人用のチャンネルを作って頂けたので、
MOD作成のノウハウや作成に関する質問や意見交換など、そちらで情報共有しませんか?