Steps:

Panel with some items (maybe also desktop)

Enter edit mode without any item selected (default properties of the items in the panel)

Change the tap action to ‘run a script’ (any script)

Change the tap action to ‘unset’

Now all items have the custom tap action ‘run a script’ instead of unset

Select an item

Click the ‘custom’ checkbox in the tap action

Now it is reset to unset, but the checkbox is still checked instead of uncheck.