I have lost count of the amount of times I have accidentally deleted an element(s) (or a container with lots of elements inside it) from a form while creating the UI, annoyingly there is no trash / restore function.
A top “undo” button in the top tool bar would resolve this headache.
It’s not so much of an issue in the code window because you can just “Ctrl + z”, but you can’t do that in the design window.