Greasy Fork is available in English.
Gets the markers_all json file and change user defined markers to be markable.
< GI AppSample Map - More Markable Markers 피드백
Update: I switched and used "violentmonkey" and installed again from there instead of "tampermonkey" and now they can be marked!
I also cannot get this to work, and I've tried refreshing, reinstalling, restarting etc. May I please get some support or tips? Thank you.