I have seen this for a long time. Just had the chance to test it more

Make a new GCV in a Driver object. Edit the GCV object, not via the
Driver properties, but from the object itself in the Outline view.

There are two tabs, first tab (General) has two lines, GCV Name (object
name) and Display Name.

I like changing the Display Name, so I changed it, and hit Ok. Ctrl-S to
save. Come back, it is back to previous value. Tried three or four
times. Tried swapping to the GCVs tab, and back, still reverts.

I know I somehow get this to work eventually, just not sure what is
going on here. Anyone else seen it?

Designer 4.5.3 (64 bit), on Winders 7 64 bit