I have found a genealogy that overlaps with mine, and I would like to brainstorm with that submitter. Is this possible, obviously with approval of both parties?
That feature has been available just about as long as FamilySearch has existed
The Help center is always a great place to find answers to questions like that
actually now that I re read your question - I might have given the wrong answer
are you referring to family Tree? or are referring to the old Pedigree Resource File - now called "genealogies"
I was assuming you were referring to Family Tree
I will see about the PRF (genealogies). - but many of the submitters of the PRF - have long been deceased - the PRF goes back various decades.
Note - Family Tree is a collaborative database - people really don't have private trees per se.
But people do have private standalone trees in the PRF ("Genealogies") section.
info about the PRF: https://www.familysearch.org/en/help/helpcenter/article/what-is-the-pedigree-resource-file