A couple users have independently complained to me about the disclosure triangle
in the save dialog; I think the problem is that apps are not recording its state
so it always has to be opened.

My suggestion is to have gtk+ save its state indexed by the app name. If the app
then also saves the state in some more specific way, then it will override the
state gtk loads on dialog creation. But per-app will already be much better than
the current situation since in practice most apps are too lame to save this.