Some years ago I made the simple sidebar template (
https://www.dokuwiki.org/template:simple_sidebar), which has a toggle that lets users open and close the side bar. However, it is based on the previous default plugin, not the current dokuwiki template. You can see it in action here:
http://www.mturner.org/fckgLite/doku.php.
You can then install the simplenavi plugin in this flexible side bar.