You can use this as a base class for your widgets instead of User Widget, and get the following behaviour:
Like Focusable User Widget (it's a subclass) this panel can opt in to automatically getting focus when it's opened, and getting it back when others lose focus.
Set the Initial Focus Widget Name to the name of a focusable widget in this panel. When the panel os attached to the viewport, this widget will be given the focus.
This widget provides SavePreviousFocus and RestorePreviousFocus methods
which can save / restore focus from one of its children as needed. They are
not called by default but are used in Menus.