OK, added to TODO list :-)

Currently, when you are in "Synchronize browsing" mode, and you navigate into a directory that doesn't exist in the opposite panel, an error dialog appears and "synchronize browsing" is turned off.

It would be convenient if, instead, the error dialog offered an option to create the directory on the opposite side. This allows me to do simple manual mirroring of the two sides, without going through the more complex "Synchronize..." feature.