Tom -
Any time I select the "Add Existing Fields" button in the Tools section of the ribbon, typically when I'm modifying a form in Layout mode. Regardless of the complexity of the form I'm editing, or the complexity of the query behind the form, I wait what seems to me to be an exorbitant amount of time (e.g. 27 seconds) until the Field List appears. Perhaps I'm mistaken about the "filtering through the entire list of every field in every table," but as my database has grown, I seem to wait longer and longer for that field list to appear, again regardless of the complexity of the form or underlying query.