There is a bug, the combo banks you create with the menu are not recognise.
Thanks for the report.
I'll fix that.
In the meantime to save your combo you can use the one from the zip file here :
http://ixox.fr/preenfm2/download/Look for "For the USB Stick" part.
You can extract the zip file to your USB stick or just copy combo.cmb in pfm2/ if you prefer.
To copy it on your USB stick, press a key while powering up your preenfm then press Eng.
The content of the USB stick should be accessible from your computer.