Currently one can drag mechanism using CTRL+ALT or with Drag Components tool. When mechanism have multiple joints one will find it hard to drag just one of them. If one could have a slider type control for each joint, then it would be much easier to control the movement of mechanism. Today one can isolate movement to only one joint using joint locks, which is a cumbersome workaround at best.
Further developed idea is to add a joint position value next to slider, so user can see the joint position in real time or possibly type in a desired value.