It would be nice if there was a option to register ssh:// as well.
I think that ssh:// would be more appropriate for SSH terminal (like Putty), not fore file transfer tool.
If not is it possible that you have a document or link that shows how to create these regstry setting from a .ini file or some other method.
Example of scp:// registration:
@="URL address: SCP protocol"
%1 in shell\open\command is replaced with URL when executing the application.
If you do not have administrator priviledges on the machine, you may replace [HKEY_CLASSES_ROOT] key with [HKEY_CURRENT_USER\Software\Classes], but the registration will be valid only for you (not other users on the same machine).