There's a discussion about custom parties over at
https://forums.larian.com/ubbthreads.php?ubb=showflat&Number=876079 so I'd suggest that any discussion of changes to the base game to support that are kept to that thread.
I'll leave this one open, though, in case anyone has a view on the specific question conmcc asked about whether the workaround available on PC (pretending to create a multiplayer party) would also work on PS5.
I've moved the thread to the Help, Tips & Tricks subforum where it seems to fit better, though.