I know it’s been a while, but I’m writing this response for those who may have encountered a similar problem today.
First, I create a “HandRSocket” socket
Then in the Mesh I create the sphere “re” and physics constraint “PC_RightHand”
Now the most important thing, in Parent Socket we write our socket “HandRSocket”, in component #1 we write the name of the sphere “re”, in component #2 we write the name of the Mesh “CharacterMesh0” and in Constraint Bone 2 we write the name of the desired bone, in my case “hand_r”
After these steps, a red and a blue cube should appear in the viewport
And at the end we get this result
