The Skin tab: paint the weights of your baked creature
Fix the skinning by hand, with a brush, on the real weights of your bake.
Automatic skinning gets most creatures right, but not every fold and seam. The new Skin tab opens once a creature has been baked and shows the bake's own weights, not the quick approximation the animation preview uses.
Pick a bone from the list or click it on the model, then paint with add, subtract or smooth. Radius, strength and falloff are sliders (Alt + wheel and Ctrl + wheel while painting), and Mirror L/R paints both sides at once. Switch to Pose to bend the rig while you paint and see the effect.
Your fixes are saved as a separate layer on top of the automatic skin, so tweaking a joint and baking again keeps them.