As a big fan of Monks and D&D, Baldur's Gate 3 is a dream come true. It's motivated me enough to actually learn a bit about modding and so here is my first one: Way of Sun Soul from "Xanathar's Guide to Everything." 

This is more of an adaptation than strict RAW implementation as Sun Soul is widely regarded as one of the weaker subclasses in Monks. So I've changed a few things. 

Way of Sun Soul

3rd Level: Light
You learn the Light cantrip.

3rd Level:  Radiant Sun Bolt
You gain a new attack option you can use with the Attack action, the Radiant Sun Bolt. It is a ranged attack that deals Radiant Damage and scales with your Martial Arts die. When you take the attack action with a Monk Weapon, unarmed strike, or radiant sun bolt, you can fire another radiant sun bolt as a bonus action.

Additionally, as a Bonus Action you can fire two Radiant Sun Bolts for 1 Ki point. 

6th Level:  Searing Arc Strike
You gain the ability to cast the Burning Hands spell with your Bonus Action for 1 Ki point.

Additionally, you can choose the damage type between fire or radiant.

9th Level:  Improved Searing Arc Strike
Your Burning Hands spell does 1d6 more damage.

11th Level:  Searing Sunburst
As an Action your can create an orb of light and hurl it at a point where it will erupt into an explosion of light that deals Radiant Damage and potentially blinds all creature in the zone. On a failure they take 2d6 radiant damage and are blinded. On a failure they take half damage.

You can empower this ability, dealing 2d6 more damage per Ki point spent up to a maximum of 3 Ki points.
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Best used with Baldur's Gate 3: Mod Manager.

Special Thanks:
Delth
How to train your wagon
Airavat
Azrael
Fae
Kvalyr
The Larian Studios Discord modding community.