Consider adding an option or even default behaviour (which should be an easy trick to do) to close formerly opened sidebar panel if user clicks toolbar icon again.
Actually the same behaviour (closing the sidebar) is expected after pressing keyboard combo once again.
For example, Ctrl+B opens Bookmarks panel and closes it as well.
Dear Danny,
Consider adding an option or even default behaviour (which should be an easy trick to do) to close formerly opened sidebar panel if user clicks toolbar icon again.