- Instead of checking for Key::UP, Key::DOWN, Key::PAGEUP, Key::PAGEDOWN etc., we rather check for the action like 'ui_up' or 'ui_down'.
- Also use AcceptDialog's 'register_text_enter' functionality to consistently close a dialog when ENTER is pressed while the LineEdit has focus (instead of redirecting ENTER keys to e.g. the underlying Tree).
- Unify the LineEdit filter behavior for the SceneTreeDialog and corresponding usages
- Improve OK Button disablement (something should be selected)