Solved!
For anyone intrested in the solution:

Should have been obvious...

There is a really helpful official steam guide for DD modders https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=819597757
Or simply google: steam darkest dungeon modder guide

Sadly I think that Conditions are hard coded
Maybe someone way more experienced than me can proof me wrong but by just looking at the code within the game it would be a mammoth task if it were possible.

On the topic of confusion: Changing enemy AI files may make something like that possible with a lot of workarounds.
The captor functionality (hag cauldron) makes it possible to exchnage an enemy with a compleatly new one or an edited one like exhanging briggand_blood_A with a custom made briggand_blood_D (check out the absorbing blob mod for reference) which may be helpful since it makes it possible to change an enemy AI during combat

I recommend starting a new file to play on and enabling the mods one by one
or alternatively disabeling mods one by one until you find the cause of the crashes
Crashes are in my experience mostly caused by a mod that won't function properly instead of compatibility issues

You need to rename some words within the atlas file as well
Use an editor and replace the hero name in the first line with your own hero name

For example: the first line within the jester.sprite.idle.atlas files is so you have to edit it to read YOURHERONAME stands for the name of your hero.

if there are still problems after that I recommend spellchecking your mod files for typos misplaced brackets and missing commas
Hope that helps :)

I'm trying to add an enemy that is forced to use a specific skill when a hero has the "Deaths Door" status with the death doored hero as target.

I know that "effect_key_status_skill" exits but I don't know if or how you can apply it to "deaths door" instead of "tagged" or "bleeding".

TLDR: Is there a keyword for "at deaths door" which can be used by enemy AI?