Trying to create a sort of custom parent constraint in KineFx, But I can't for some reason figure out how to compute offset and still have the parent control the child. I have to do an inversion and it's canceling out the transforms. In the file attached, the green cone should be controlled by the red cube but notice if you adjust the cube, nothing happens. How can I fix this and maintain the offset with a custom solution; I really need some help with this! many thanks in advance!!!

one of the ways is to stash rest_transform before the rigpose and use that to compute offset from
since after you move the red cube in rig pose you otherwise wouldn't know what the offset was