According to TWiki:Plugins/TopMenuSkin
If you want a sidebar in addition to the top bar, define a WEBLEFTBAR setting with the name of the topic to include as the sidebar.
This can be done in a WebPreferences for the whole web or in a topic. Example:
* Set WEBLEFTBAR = WebLeftBar
There is no easy ay to re-hide the left bar if, for example, most of a site wants it but one or two webs do not.
May I suggest supporting the following:
* Set WEBLEFTBAR =
as a simple way of toggling this setting.
(At present, this syntax throws an error).