Negative sidebearing for non-spacing accents?

I wanted to have my accent marks as combining, but also as a fallback when an app/program doesn’t attach the anchors. Is it possible to give negative ‘sidebearing values’ to non-spacing marks on export while still easily editable when working in Glyphs? (Or what can be a better approach in this scenario?)

(right now I noticed while zero-width, they just have the same left side bearing throughout)