Ability to turn "undo" off and on

It would be really nice to have the ability to make visibility of the undo button, or any toolbar button, conditional on a global property, or grayed out on a key command, or similar.

A dual or multi-state choice of image would be nice for any toolbar button - not just for on or off but to allow the state of any variable button to be shown. Maybe something equivalent to the “Layer” trait, so that the state of the button can be easily set and interrogated by the module; in which case no image might make the button disappear (not sure if that would be feasible).

There is one button that has a dual state implemented - the LoS Thread - though I haven’t seen the second image working yet.

I second the ability to toggle toolbar buttons. There are dozens of instances in my modules in which it would improve the UI experience. It would also be great to be able to refresh or close GPIWs with a command.