Closet thing you got is the InvitationMod Manual. If you want anything abit more custom like custom made passives then its cold turkey mostly. There are minor guides that tell you the basics on steam for coding using visual studio, but anything like custom effects and greater, there is no real guides unless they are hiding on discord/forum or in a different language .
Link to InvitationMod manual: https://docs.google.com/presentation/d/1WGBglM3IR4d8ZPd4xRyyx_cyl8nrsHQmQnGx6FOIiDk/edit#slide=id.gecc2b7d568_3_0
Link to making custom Models for keypages manual:
https://docs.google.com/presentation/d/11T9-2mE2H6u080ugyT_QL0nmNG76x2uM8899SwUBP3M/edit#slide=id.g87c1482c33_0_0

I'm pretty sure I overlooked this Invitation Mod. This may be more than enough for me to do what I wanted to. Thank you very much!