sharepoint online – Using multiple groups for “People or Groups” column

I have a SharePoint group of people that have a certain access in the system (let’s call the group “Verified”) and a form field (“User”) that references this group so that submitters can only choose someone in that group. The issue is that the “Verified” group is now over 8000 people and it won’t let me add any new people, but more people are getting access every day. Our SP contacts say it is a Microsoft limitation.

If I were to create a second group (“Verified2”), is there a way to merge the 2 so that the “User” field will allow anyone in either of the 2 groups to be selected? I’d rather not make that field open, as there would be no validation that the person entered in the field has the appropriate access.

Also, I have a query in Excel that pulls everyone in the “Verified” group. if I create a second group, can that query be updated to pull everyone in both groups, or would I need to create a second query?