In the Customize dialog, the 'Function' list in the 'Toolbars' tab shows checkboxes where the user can activate and deactivate items from the list. This is really handy because the user must not delete and re-add them.
But the 'Function' list in the 'Menus' and 'Context Menus' tabs doesn't have checkboxes.
Add checkboxes to the items at all function lists.
Don't see a need for unchecking menu items. The toolbar has an extra "customize" menu where users can toggle items on/off, which is the same as checking it at the customization dialog. But menus do not have such a feature, and will never have it. Clearly a WF.