[Solved] filter for certain groups / users in the recipient list

Hello!

I would like to have only those users suggested in the PM list who are also listed in the member list.

For example, there is the group "Forum users" with the option "Show in member list" and another group "Forum users without member list" - which are then not displayed.

This second group should therefore not be included in the list of PM suggestions.
I could do this via PHP with an exclude using the groups.ID, but would need a tip where this would fit in which PHP file.

Or can this also be done more "smoothly", possibly as a new feature?

THX