I would like to add a new session to the login screen (the thing where you select "Ubuntu, Ubuntu Classic, etc" to install a new GUI on. How can I do this?
The list on the logon screen is populated from the desktop files in the folder
The format of these files are similar - here is the Unity-2D desktop file
All the files are root:root owned.
Creating or deleting desktop files in this folder creates or removes an entry in the drop-down list respectively.