Saw something somewhat similar as an idea (mass update fields to hidden across forms), but not this use case exactly.
Would be great if I could select a field and mass add it to forms in Marketo. I have 40+ forms that are all using the same bucket of hidden fields that get populated by an add-on, so it would be great if I had a new field to add I could just do it to all those forms at once rather than one at a time.
Same principle for removing fields. If I have an old field no longer in use would be nice to be able to just remove it from all forms at once.