hi @jhera,
there are multiple ways to build accented glyphs in RoboFont. these are described here: Building accented glyphs
have you tried using the Glyph Construction extension?
in 2019 you don’t really need anchors to position diacritics anymore :) you can still use them (with or without underscore), but you can also use guidelines, variables, vertical metrics attributes, reference positions, etc. have a look at the docs & give it a try!