Ubuntu – Set default user session to XFCE4

I initially tried editing /usr/share/applications/vim.desktop. I commented out #Exec=vim %F and added Exec=xfce4-terminal -e 'vim %F'. This worked for a while and then it started opening both Xterm and Xfce4 Terminal.

Instead in Thunar I right clicked on a txt file. I went to Properties > Open With: > Other Application > Use a custom command. I added xfce4-terminal -e 'vim %F'. This now works perfect.

To access the .desktop file you just created you can go to ~/.local/share/applications/. In the file you will see Exec=xfce4-terminal -e 'vim %F' %f. You can remove the %f if you'd like. Mine initially used a folder icon in Thunar. I changed it to use the Xfce4 Terminal icon instead by adding the line Icon=utilities-terminal.