When I was done creating the new "Lid_Follow" property on the "Eyelid_Bottom.L", I, out of curiosity, moved my mouse over the newly created value and hit backspace. I was thrilled when it set itself to the 0.15 value that I had given as the new default value for the bottom lids. So when I copied "as a new driver" and pasted the driver on the "MCH-Eyelid_Bottom_parent.L" constraint, the value automatically showed the "0.15". I didn't have to backspace over this constraints value to reset it again. Since I had never known this was possible, I thought I'd share, in case, anybody else doesn't know.
