I ran into problems with kerning exceptions in fractions only (kerning exceptions in other places work). Glyphs App displays the fractions correctly, InDesign kerns too much where the locks are open. I tried in different InDesign files. For now closing the locks or creating a new kerning group helped.
Yes, I use the Fonts folder. So far it worked out well to have the superiors assigned to 4 groups: zerosuperior, onesuperior, foursuperior, sevensuperior. But anyway, creating exceptions in fractions shouldn’t create problems. Or is that tricky?
I would rather give every denominator figure its own group, then reuse the groups for the numerators (i.e. one.numr and one.dnom share the same groups). Then group kerning between the small figures and the fraction slash suffices. I never needed exceptions for small figures.