Undo redo support has not been added yet. Since yesterday, I have been exploring the same. Implemented a part of it by looking at undo redo implementation in Selection Sets. Some things look clear, others fuzzy. Since mid-term is near, I considered starting my last milestone before it. Little late for it. It is adding and removing objects from selectors via use of symbols in front of each row of treeview. Adding this new feature is huge.
And meanwhile today, I found another issue in implementation done so far. Yep some trivial but significant cases always hideous. Remove text from the entrybox which is used to set the name of selector and a crash. In this case, I set default text .Class1 for the selector name.