OT Features (at least stylistic sets)

[Mark2Mark]

Would it be too much to ask for this? It would be really helpful especially for complex variable fonts in development to compare different ideas that are tossed into different stylistic sets.

[dberlow]

This could be a menu in the left column
that activates if features are in selected font,
lists those features In menu,
and turns the selection on everywhere if nothing is selected,
or turns on feature on in selected text?

[Mark2Mark]

Globally would be fine.
Toggling features for only a portion is probably a too specific and rare use case, I can imagine?