What are you calling the top-most node/person?
Your oldest ancestor?
Sort People view by birth date then run an ancestor filter. The first (or last depending on sorting order) will be that oldest ancestor (if birth date have been entered).
I don’t have this issue because of my numbering/ordering system, I just sort people records by Gramps Id and it’s done. The greatest IDs give me my oldest ancestors.
or retreiving last ids with a simple regexp filter:
