As i worked with shapekeys for the left and right leg, i can easily mirror shapekeys. This shapekeys are connected to a driver. One for the left side and one for the right side. For better control of the driver i use a custom curve, which is identical for both drivers. As i adjust one curve, the other is still unchanged. So i will have to synchronize them again and again for finetuning. Can this curve be shared between multiple drivers, to avoid this?
You can certainly drive one shape key with the other. If you have curve for leftleg add a diriver to the rightleg shape key value slider then In the drivers editor add a var … make it a single property, select keys, your keyset (I think that is what that is) name probably “Key” then the path to the value property which will be something like keys[“leftleg”].value
Use the debug checkbox to see you are getting the correct value.