How to remove reference to disabled 3rd party Excel Add-ins (NOT COM add-ins!) from menu

This is for Excel 2016.

I did find this amongst a hundred other web results regarding the removal of COM add-ins, which I figured for myself, there's a handy remove button right in the menu:

However, there is no such button for the "Excel Add-ins" menu, the button for which is adjacent to the COM Add-ins button:

I can deselect it of course but that doesn't remove it from the list, even after restarting Excel.

So, how do I get rid of them?

if it helps, these were/are .xla add-in files on a shared drive, so I can't just delete them.