8 – How to pass a field value from a parent node to its entity referenced children nodes when saving the parent node form

Drupal 8

Here is the scenario

I have a Company > Department > Employee… in that hierarchy.

Companies are already created previously.

On the Department node add form, there is an entity reference field to reference a Company. On that same Department node form, there is another Entity Reference field that leverages Inline Entity Form to add + reference Employee nodes on the fly. These Employee nodes also have a Company entity reference field.

The goal is to pass the Company field value from the Department node to the referenced Employee nodes when the Department form is saved.

I figure this may be accomplished with the Business rules module, and/or a hook form alter. Tried both without any traction. Any tips?