It would be nice, if it was possible to expand/collapse a branch by doubleclicking the topic. It would make it easier to navigate maps and is more natural than having to concentrate on hitting the "+/-" icon.
I believe it was added in MindManager 2012. It's definitely in Mindjet 11. Go to the file menu, select Mindjet Options. In the edit menu, uncheck the option "double click selection frame to format option".