I'm just learning about shape keys. I created two shape keys, the basis one and one with the tip of the finger bent. I added the bone of the tip of the finger as a driver. It works but, the changes I made so that the bent finger looks better make it so that when it's going back to its original shape it doesn't look quite right. How can I edit the in-between shape?
Shapekeys are not a very solid alternative to rigging. The way shapekeys work is by exclusively translating each vertex from the Basis to the shapekey. The shortest way to do this would be by translating each vertex in the way you see in your "in-between". Shapekeys should only be used for things such as facial expressions, correcting armature deforms, etc. In short, the inbetweens cannot be controlled, you're going to have to rig that finger if you want it to move correctly