Add new custom theme to Frappe core app

Hello everyone, I’m trying to add a new theme to the Frappe core app so that all of my other apps inherit it, but I’m really struggling with it. is there anyone who can help, please!!

for the love of god, i can’t seem to figure out why my .scss file is not being compiled. i’ve added it in the same foler as dark.scss but mine is not compiling. and when i did a codebase search for dark.scss to see if it’s being included or imported anywhere, i don’t get any results. so dark.scss is never mentioned anywhere in the code, yet it’s being compiled. help T-T