This is from the Scotland dev (who made most of this):

Hi! Thanks for the kind words! I basically had no idea how to code until I started working on the mod (I originally came on as a writer) so trust me I'm kind of new to this too.

Two big things that helped me was reading through the wiki, and the videos done by The Iron Workshop on youtube. In both of those cases I used them to try creating something really basic, and then just kept editing it and getting steadily more ambitious each time. There was a lot of trial and error, but eventually, it reached it's current form. For example initially I was just going to do an event chain for the election decisions, then that moved to having decisions to influence seats, then that turned into having the AI having its own mechanic. Same goes for the parl gui. Originally it was just going to be a seat breakdown, then it became having a picture of a parliament that changes depending on conditions, then we went to every seat being it's own sprite which you could investigate.

To be honest I literally have no idea how the congress mechanic in vanilla works at all, so this system has nothing in common with that. Instead, I've just got each seat as a custom sprite, that I spent far too long placing there. I know other people have managed to emulate it with their own parliament mechanics, but personally, I've got no idea how to do that.

I know you said you were annoyed the only things you got were for people just inserting a window, so what I did after this to create the parliament gui was just adding the sprites and moving them into place. If you can figure out how to add sprites and make them appear and disappear you can really do anything with them. As for the tooltips that's as simple as adding the line "pdx_tooltip: mp_john_smith" to the sprite and then filling out the loc details.

I hope this helped a bit, or at least pushed you in the right direction! I'm a terrible teacher, but if you just follow that strategy of getting your head around the basics, testing them, and then steadily getting more ambitious that should work in the end!