Evaluate Changes in Collection: Added or Removed Items?

Dear experts,

I am looking for an efficient way to identify changes in a collection which then would trigger an action in an beforeSave event.

Actually the action should be triggered for each added item in the collection and another action should be triggered for each removed item in the collection.

I know that to track changes of single field values can be done using an additional extension field which always stores the value prior to a change.

However for a collection I have not found an efficient solution so far.

Any recommendations how to handle this?

Thank you for your support & ideas!