Create a helper skeleton that can be used to adjust the position of skinned joints.
The edit skeleton can be moved and rotated, like editing a skeleton in Move Skinned Joints mode. However, the bind skeleton can be freely posed while doing this, to quickly see the results of adjusting joints.
When finished editing, just delete the editable joints.
Select one or more joints, and Skin > Create Editable Joints from the Rigging menu set.
It's useful to enable Preserve Children on manipulators to move a joint but leave its child joints in place.