There are a couple of things that are very common that I would like to add buttons for. The first is for clearing the value and the second is a + for adding new items to the list. The + button is an important one from a usability standpoint. Quite often the combo/dropdown is populated from a list that is managed on a separate page. It is too cumbersome to have to use stop entering and go to the admin page to add the new item and then come back to add whatever they were working on previously. I know I could simply add a button beside the widget but this just doesn't look as nice as it being built in.