Some genealogy products such as
TMG do allow
Relationships to have
Source Citations, but they do NOT export in
Gedcom nor migrate into
FH. I don't see why a spreadsheet cannot record relationship assessments. Some people use hand-drawn diagram techniques.
In
Knowledge Base > Recording Credibility of Family Relationships I have suggested
four techniques, not just
Flags. I would not call
Flags the
closest because they apply to the whole person not their relationship, which is why I list them last.
They all export in
Gedcom, but the
Witnesses and
Flags use custom tags, although the
Export Gedcom File Plugin converts them to standard
Gedcom. The
Parents Family Note Citations and
Associated Persons Citations use thoroughbred standard
Gedcom features.
Checkout the
Wish List reference for some observations from others. Perform a Forum search for
surety and several other ideas and opinions are forthcoming. I have added these links to the KB article.