[Graion Dilach]

EET_NPC_TRANSITION is kinda annoying when you want to add something of your own in there because from what I know you can't add stuff of your own: your own checks and/or actions.

AFAICT, as long as you don't touch/offset that one dialog state where the list comes up, you can extend the dialogue. EET_NPC_TRANSITION does a DECOMPILE_AND_PATCH underneath, so an extension which ensures that one point remains unchanged would do.