Subclassing Widget Templates?

hI, I tried but can’t see an option to make a child of a widget template. Is this not possible?

What I want to do is make a button template, then make children of it for menus and for other ui elements. I tried making a new ui widget and reparenting it but then I get a blank widget and need to re-do all the template anyway. So do I just need to make one then copy it and not bother with parenting?