Use ~ in the folder path to refer to the User Home Directory ($HOME or %HomePath%)1).
applications List WWWBROWSER, MAILCLIENT, OFFICE, TERMINAL dito List of generic commands offered by X2Go Client / Pyhoca-GUI for quick-launching. Commands are handed over to the server script x2goruncommand which then decides what application to launch.
Setting the command to RDP will turn X2Go into an RDP proxy (RDP via NX). RDP will receive a performance improvement on WAN connections and X2Go will guarantee SSH encryption (whereas RDP drops encryption if the bandwidth won't suffice).
Make sure to use the options rdpserver and rdpoptions properly.
Do an XDMCP query for the XDMCP server specified by the xdmcpserver option. Useful if you have a complex terminal server setup behind one X2Go gateway (e.g. handled by an XDMCP chooser).
Specify any application (by its name) that is available via $PATH. No full path names are allowed here, the path will be stripped off of the file name provided. Make sure your $PATH environment variable resolves to the wanted application properly.