OK, I need to sync the toggle behavior with the state of the wiki explorer. It's a bit more tricky in a multiple document scenario because there's only one ribbon(displayed several times) and a separate pane for every Word instance.
What do you think it should happen when closing one of the wiki explorers?
1) Closing a wiki explorer means closing the wiki explorer on all Word windows -> The button has the state for all the panes
2) Closing a wiki explorer does not affect other similar panes -> The button only has the state of the wiki explorer corresponding to the active window. When switching to another Word window the button takes the state of the pane for the new Word window.