I would love to be able to keyframe the parenting option. Sometimes you need a layer to be the child only for a fration of the time, than be released and continue with it's own animation: for example a charakter that lifts a cup, trinks and than puts it back onto the desk where it slightly slides into it's restposition.
This is just one of many possible options where it would be nice to keyframe the parenting option. Right now it is only possible via a bit of expressions or a 3rd party script that uses a workaround but it should be way more simple!
It is not as easy as Gabriel says. If I apply a bezier to an object after the null parent ends the bezier is applied to the object within the parent. I do not want that to happen.
Gabriel Barbosa commented
There's a easy way to do this that doesn't need plug-ins and expressions. You can create a null, parent this null to the where you want it to move (i.e. character's hand) and adjust its layer duration to be only when the motion happens. Now parent the cup to this null. If the cup is already parented to another null, then parent that null to this newly created one. You can chain them as much as needed like this.