Answer

There is no key combination to disable the touch pad on the ThinkPad X121e.

You can however enable or disable the TouchPad in two clicks, if you enable the ThinkPad UltraNav icon in the taskbar (from the Mouse in Control Panel). Check the UltraNav utility to do the settings for your touchpad and trackpoint. This info can be checked from X121e user guide.

A workaround suggested by a member of the community is to leave the TrackPoint enabled all the time so that when a bluetooth mouse battery is flat, the trackpoint can then be used to re-enable the touchpad.

Note: If you have issue with the touchpad when typing, you may want to check on the new feature called PalmCheck for touchapd and trackpoints.