[whpalmer4]

If you are "setting a priority" by using the flag, you can flag the project instead of all the contained actions. Until you unflag the project, everything in it will be treated as if individually flagged, except you won't be able to unflag individual actions.

Alternatively, do a group selection of things you want flagged, then right/ctrl-click to get a contextual menu that will let you set/unset the flag for the whole bunch at once.