Hi!
Add the ability save (and optional bake) custom expression in the Face key editor. See workflow below.

1. Use all the Face key editor features to create a unique "Face Expression".

2. "Click save as Custom Expression", [now to the important stuff], add the option here to save as baked expression. If save as baked is used, a new "real" morph target is created from all the used targets. Non baked Custom Expression is of cause parameter driven using you standard morph targets like the one you already got...

3. With the ability to bake and use "Custom Face Expression" its easier to use them in a game pipeline later on as your full system with +70 morph targets is not optimal for games, where limited platforms only support approx 8 simultaneous morph target in HW.