I checked what is possible and what you ask should be doable. However, ONLY for the topbar items! (otherwise I will need to completely rewrite the navigation bar and frankly I don't have the time for this now).
I can write a method like this:
page.NavigationBar.UpdateTopbarItemEx("LogOff", "mdi-action-delete" , "[" & counter & "]", ABM.COLOR_GREEN, ABM.INTENSITY_NORMAL)
If that is ok for you, add it in the feedback app and I look into it.
This is already in the feedback app and will be handled in a future version.