It's a small utility I have made for myself and I'm sharing it in case anyone would find it useful. Basically every time the Dragonborn's relationship with any NPC changes, you receive a notification. That's it, no effects on gameplay. Might be useful if you're roleplaying a Dovahkiin with high emotional intelligence lol. It's an ESL-flagged ESP so it won't count towards plugins limit.

Warning
Before a more detailed description I'd like to stress that I'm a beginner in modding and this is my first mod ever. I tested it on my clusterfuck of a load order (565 plugins) and it didn't cause me any trouble, but I can't guarantee anything. If you'd like to test it, please make a backup of your save.

More details

In short:

• Main file - adds notifications when relationship ranks change in the background (for example as a result of a quest);
• Optional file - adds additional info when you activate an NPC.
  

The files are meant to complement each other. If you want both functionalities, you need both files.

This mod was built and tested on Skyrim SE 1.5.97. I did not update to Anniversary Edition, therefore cannot test it in AE.

Main file
There are no scripts running constantly in the background, there is only one small script activated when the OnStoryRelationshipChange event fires. Doesn't matter if it's triggered by a console command, some kind of mod or a completed quest. You'll see a notification in this form:

<NPC's name> is now my <relationship rank>!

If your previous relationship rank with this NPC was lower, the notification will be preceded by a + sign (- sign if otherwise).

Optional file
Optional file allows receiving info about current relationship rank with an NPC at the start of dialogue with them. You'll see a notification in this form:

<NPC's name> is my <relationship rank>.

(slightly less enthusiastic than in the main file lol)

From v1.1d-beta the optional plugin also shows whether the NPC belongs to PotentialMarriageFaction. Note: additional steps may be required for marriage dialogue to show up. My mod only checks if the NPC belongs to the faction. The notification is as follows: 

It seems <he/ she> is available to be married.

If you find this wording super awkward (I had no idea how to make it sound better), it's easy to change it in xEdit. You can turn this feature off completely by typing in the console set RNND_MarriageNotifications to 0. 

From v2.0d-beta the optional plugin also shows the NPC's disposition toward the player based on their faction (Faction reaction - CK wiki). It may feel a bit redundant considering that it rarely differs from the actual relationship rank. That's why it's possible to turn it off with console command:
set RRND_FactionReactions to 0.
Notifications for neutral/ friend/ enemy reactions:

<He/ She> seems <neutral/ friendly/ hostile>.

(From version 3.0.0d the notification has proper capitalization.)

Notification for ally reaction:

We are on the same side.

Since the updates have brought many new options to configure, the v2.0d-beta update includes MCM to makes things easier. Configuring the mod through the MCM is the same thing as doing it through console commands. It's there for convenience.

Version 3.0.0 is another big rework of the mod. I'm dropping the beta tag since the mod is now much more mature in my eyes.

• This update removes hard SKSE dependency: SKSE and SkyUI are only required if you want to be able to configure the mod through the MCM.
• Instead of listening for events in the script, activation of the NPC is detected via perk  - big thanks to lofgren for the suggestion.
• All notifications are now properly capitalized - big thanks to gmiller7138 for the suggestion.
• The mod has now three ways of configuration: the MCM, console commands, and the Relationship Insights power.
  

Console commands reference

• The config power can be removed from the config menu it invokes, through the console command or from the MCM. It can be added again through console commands or the MCM. Everyone should be able to find their favorite way of configuring the mod, with SKSE & SkyUI or without.
• The new advantage of using the perk system is that you don't have to enter the dialogue with NPC to get the notifications. All you have to do is activate them. Therefore even if the NPC doesn't have any dialogue lines, the perk will work.
  

More technical details:
I tried to implement the optional file in the same manner as the main file, but - no matter what I tried - the Player Activate Actor
story manager event would never fire and therefore my script would never run. It just doesn't seem to work. The one and only post in the discussion on the Creation Kit wiki seems to confirm this problem. I had to change my approach.
In v1d-beta:
In v2d-beta:
Version 3.0.0d is much less complicated, it uses mainly the perk added to the player.

Possible relationship rank values (Creation Kit wiki)

Requirements
Main file
Something I totally forgot about earlier:
SKSE is needed, because I use GetName() function in the script to retrieve the NPC's name. I'll look into making a version without this requirement.
As of version 1.1
I reworked the mod to work without SKSE. The mod is now more proper, as the script itself is even shorter, operates on Message objects instead of using Debug.Notification() and is more translation-friendly (translating will require editing only the plugin, there is no need to recompile the script). NPC's name is retrieved through Quest Alias instead of SKSE function.

Optional file
Older versions:
Version 3.0.0d  removes hard SKSE dependency. SKSE & SkyUI are now optional and only needed if you want to configure the mod through MCM. No other requirements.

Compatibility
I haven't found any incompatibilities so far. The incompatibility could arise if another mod changes event nodes in Relationship Rank Change node in Story Manager. The quest node added by my plugin doesn't consume the event - it's propagated further, but if the record gets overwritten by another plugin then in the worst case scenario my script will simply never fire. It's easy to look for conflicts in xEdit, my script doesn't modify any vanilla assets or anything like that.

Translations

• Translations hosted on Nexus are available in the "Translations" dropdown at the top of the description.
• Additionally a ?? French translation created by Elmeridyn is available here - La Confrérie des Traducteurs.
• Many thanks to the translations' authors.
  

Updating
Main file
It should be safe to simply overwrite the previous version, I tested it on my load order and it didn't cause any problems.

Optional file
Older versions
Updating from <v3.0.0d to v3.0.0d

There are 2 ways:

1) You can simply overwrite the previous version and then - either through console commands, config power or MCM - restart the mod for changes to take full effect. Otherwise the notifications won't be showing up.

• Restarting through MCM: open the MCM, disable the mod, close MCM for changes to take effect, open it again and enable the mod, close the MCM for changes to take effect. Done.
• Restarting through the config power: activate the power, click on the "Mod is ON" option, then click again on the "Mod is OFF" option. Done.
• Restarting through console commands: type in the console set RRND_ModEnabled to 0, save the game, load the save, type in the console set RRND_ModEnabled to 1, save the game, load the save. Done.
  

2) You can uninstall previous version, make a clean save and install the mod from the beginning.

Updating from v3.0.0d to v3.0.1d or v3.1.0d
Safe to simply overwrite.

Testing in game
Main file
If you'd like to check it out in your game immediately after installing, try to change relationship rank of some random NPC with a console command.

• You should probably make a save first.
• Open console with the ~ key.
• Click on an NPC to target them in the console.
• Enter the command: setrelationshiprank player <number from -4 to 4, refer to the link above>. If you'd like to check your current rank before changing anything, use the command getrelationshiprank player.
• Close the console, you should immediately see the notification.
  

Optional file
Notification should show up when activating any NPC.

Uninstallation?
Technically you shouldn't uninstall mods with scripts in the middle of a playthrough. The scripts in this mod (both main file and optional) aren't invasive and when I tested uninstalling, it didn't broke my game or anything. But I can't guarantee anything.
If you want to uninstall the optional file, I recommend using the "disable the entire mod" option and removing the config power from your magic inventory. It simply stops the mod's main quest and removes the perk from the player.

If you decide to uninstall a mod with scripts in the middle of the playthrough, it's a good idea to use FallrimTools ReSaver to remove any leftover unattached instances from your save.

I know this was a very long description for a very unimportant little mod, but this is the first time I'm publishing anything like that.