Are you writing about the gearschift lever or about the rear gearmech?
My way of protecting a rearmech when boxing up a bike for taking it along on a plane, is quite simple.
I unschrew the rearmech from the dropout and let it hang under the rear chainstay. (I tie it up a bit with a bit of string, or in the past I have used a pedalstrap). I also reverse the pedals!
When reattaching it, the adjustments of the gears will be the same as before when I detached it.
If packing a bike with the wheels removed, I put dummy axels between the rear and front dropouts to prevent bending of the frame or of the fork.
Dummy axles can be made from left over wheelaxels.

Ralf