Maybe I'm missing something in your question... what you seem to be asking for is the reason groups are available in the MMGT, and they work for me.
In the editor, select the Buttons tab and double-click on one of the IA buttons you want in a group. On the resulting page, at upper left in General Settings, there's a pull-down called Group. Pull down and select a number for the group you're building. Click Done. Double-click on another button you want in the group and do the same thing, giving it the same group number. You'll now have two buttons in a group, and selecting one on the MMGT will de-select the other. Add more buttons as needed, only one button in the group can be on at the same time.
Is that what you're looking for? Not working that way?