Simulate parenting, (or un-parent) in after effects
The only solution to do this without an extra script/plugin is to use expressions and then convert the expression to keyframes via Animation-&gt;Keyframe Assistent-&gt;Convert Expression to keyframes.

The big downside is that you have to "build" the parenting yourself, if you parent the position of one layer to another it will result in an expression like: thisComp.layer("Black Solid 2").transform.position. You then have to manage your relative position manually by changing the anchor point which is tedious, then you have to basically parent each transform property manually if you want rotation, scale and opacity as well.

So unless you can't spend the 15$ or can't use plugins for any reason I would always go for the script solution.