It looks like a bug to me. In addition, the ALT+TAB is one of Windows reserved shortcuts.
I see a few ways you can fix the problem:

Open menu as a table, find the record with ALT+TAB and replace with ALT+5

Write a simple driver for GenMenuX that will change ALT+TAB to ALT+5

Use a ProjectHook to do the same.

>Whenever I try to assign the hotkey ALT+5 to a menu option, it assigns ALT+TAB. I can change it in the MPR and then it works fine. But of course, the maintenance will pose a problem, because there's no easy way to remember this manual adjustment over time. Anyone here familiar with this quirck?

--sb--