I have an add-in that adds a toolbar to acrobat. This toolbar contains 3 buttons. Based on the active document, some of these buttons should be visible, and others should not be.
When I add the button to the toolbar I am using the AVToolButtonSetCompteVisibleProc function to set my visible callback. In a very simple example I have set my callback to simply return false. When debugging the code, I can see that this callback is called, however the effect is that the button is disabled, not hidden.
The version of acrobat is Acrobat Pro DC Version 2018.011.20063
As of Acrobat X, when we went to the more modern toolbars, we dropped the whole concept of hidden buttons and instead just enable/disable them.