How to limit entity reference for new nodes only? In an institutional website, there's an archive section listing all events (content type: Event). Each event is coordinated by an event manager (content type: Event Manager). CT Event has an entityreference field to select an Event Manager. The available options are defined by an entityreference view. This process works well so far.

Next, I needed to limit the available managers depending on their status. The status is a simple boolean field in the CT Event Manager defining if that manager is still active or retired. This limitation also works such as new events can't be assigned to retired managers.

However, if I want to edit an (old) event which was managed by a now retired manager, I can't save the node since the reference is not valid anymore.

My question is, how can I restrict the number of available managers for new events but still maintain the relations between old events and retired managers?
You need to render views in the Entity Reference field. 


Add a reference type display in a view.
Add a nid and title field in the view.
A list of views will be displayed in the field configuration. Select specific view in field's configuration.




Edit: 

May be adding hook_form_alter to form can do the trick for you.

function hook_form_alter(&amp;$form, &amp;$form_state, $form_id) {
  if ($form_id == 'your_node_form') {
    // $form['#node'] if it is node edit form.
    // $form['reference_field']['#options'] = $altered_list
  }
}