Suggestions on the Improvement of mapping node position
I found it hard to adjust their uv position conveniently with ucupaint. I hope that the mapping nodes could be placed in the ucupaint group rather than each layer group, so that they can be adjusted easily through group input. This may also be beneficial to performance because the number of nodes reduced.
Also works with multiple uv maps:
Sorry for the late reply, mapping is a layer option so it should be inside the layer node. You can add a driver to make the mapping node use the same values between some layers but yeah, it's not something that is easy to do. Maybe in the future there will be global mapping settings, but I'm not sure how it will look in the UI yet.