An user script of general application is one which changes the background colour of some sites. Also, for facebook only, FBPurity. https://greasyfork.org/en/scripts/979-nobrighter https://www.fbpurity.com/

I use bookmarklets also to change background colour. Two are based on a script posted on reddit, two others from https://www.squarefree.com/bookmarklets/.

I'm not seeing any such posts on fedia.

Evidently, adding a tag to a bookmark enables that section. In my case it's already there.