In the fckgLite wiki, it is using indexmenu, and to see the overlay you have to click the index button. http://www.mturner.org/fckgLite/doku.php
fckgLite is no longer being supported or maintained, but the web site has a lot of info that applies to ckgedit, which replaces fckgLite, so I keep it in place.
The overlay plugin has a lot of options and possibilities. Even I have to look them over to refresh myself. But if you are using the Dokuwiki template, or one that retains its basic structure and div names, it falls right into place.