How to load relative snapping tool:

Right mouse button clicking on the button of MGTools and select "Relative POsnap Forward/Backward".

When to use relative snapping tool:

Sometime u want to achieve that the selection being parent constrained by something else.

U can use the real parent constraint to do that ,but when a great amount of other objects are constraining the object ,switching the constraint weight is kind of tricky thing to do.

So why not faking this in some situation , no constraints, just using keyframe per frame. When the constraint master's animation being changed, just faking it in several seconds.

How to do a relative snap forward / backward:

1.Select two controllers , for example , one is hand mov controller, the other one is the props mov controller.

2.Select RelativePOsnap Forward/Backward as said above, There will be a snap used locator created, and the time tick will step forward / backward for one frame.

3.Pressing G key in your keyboard to repeat this command and watching what is going on in your view port.

4.When props is going to leave the hand, stop pressing G key.

5.Now it appears like the props being parent constrained with a offset by the hand for a certain period of time.

  Notice that sometime using the actual parent constraint with offset will be time saving. This relative snap tool could be handy  when u got to switch between lots of constraint weights.

Tips : In MGTools Pro3 , select a time range before applying the snapping,  then do the snap, the object will be snapped in one go all over the range.