You need to put them in the same place renamed .arz is which is Grim Dawn/mods, without renaming them.
Should have mentioned it here but I probabably wrote it somewhere else (I’ll search now).
It should work although I haven’t tested big mods personally. Or I might have run Grim League this way actually so that new illusions were visible in Main Menu.
[edit] I wrote it here
and just added in this thread as well.