I remember back in the day there was a forum dedicated to custom TMW groups where people where sharing their groups

[hasnogaems]

Where it is now? Is it was hosted on curse?

[ascott18]

Curse deleted it many years ago, and despite promises to make the data available, never did. https://authors.curseforge.com/forums/wow-sites/wow-sites-feedback/127024-no-more-project-forums?comment=4