WP menu doesn't support character "[" and "]"

Hello,

WP menu support attribute “rel” (XFN) but, it doesn’t support characters “[” and “]” in that, which make my “animated collapse” javascript unusable. I have to add rel=”toggle[example]” to one link, but WP make after saving just rel=”toggleexample”.

Is there any way, except hard-coded menu in template, how to add rel=”toggle[example]” to a link in WP menu?

Thank you for all responds!