I use often FreeMind as a tool to help me to take decisions, or as a tool to record and semi-structured knowledge bases, which I regularly extend.
As it becomes a more common tool, and as it takes some time to get launched, I have it opened early, and open the various files I need from there.
I would therefore highly benefit from having bookmarks as in Firefox (for ex. on the same line as tabs, as we usually have less than 5 tabs open). This would allow to have quick access to all the bases.
An alternative may be to prepare a map with the links to the maps we want to bookmark; this seems a bit more cumbersome and would require the option to lock this map on the first tab to always have access to it (and it would require to first switch to the first tab in order to have access to the bookmarks).