Is it possible to use bones to make poses and then assign a shape key to that pose?

I’ve been learning to rig a head model with Rigify and the face armature with the idea that I’d be able to use poses made with the rig and assign shape keys to them. I’ve been googling for a week but have found no guide to doing this. I suspect there might be something to do with assigning drivers and bones, but can’t find instructions for this.
What I’ve been able to do is make one pose and assign a shape key to it. When I try to make the same pose on the other side the new shape key drives both poses instead of just the one side of the face I created it on. I can’t figure out how to assign just the bones I want to the shape key and leave the previous shape key alone.
I’m beginning to think I’m wasting my time. Should I just get rid of the rigging and start dragging around vertices instead? I’d be done by now.

I sense a little bit of terminology-confusion here. Can you post a .blend file?

What did I get wrong? We’re dealing with an interface here that has a button tagged “gizmos”. Some latitude is fair.
I don’t seem to be able to upload an attachment, but here’s a google drive link: