How to send a message notification based on a flagged node being linked via entity reference?
It works, after days and days it finaly works! I used this as a base line for my research: Sending a message to users of a flagged node when it is referenced

Instead of sending an e-mail within the loop, i create a new entity(action), in this case the message notification. After that i fill(set data) in the entity-created:field-mnc-recipients field with the flagging users. This is how it works :)