Options:

You can basify a plane in order to "break" the associativity by using the Others > Basify contextual command. In this case, when the plane's reference face is going to be moved (change of part's height) the plane will remain in its initial place. If the plane is not basified, it is going to follow the face's displacement.

Additional information:

If the entity on which a non basified plane relies is destroyed, the plane becomes invalid.

The planes created are grouped together in a Planes folder of the entities tree.

From this folder it is possible to edit, delete, rename and hide/show the planes using the popup menu.

Editing a basified plane from the entities tree, allows its bounds to be changed by modifying the min and max X and Y values, or by sliding the handles on the plane.

A non basified plane can be replaced by another plane from the entities tree.