Multi-Entitiy field creation

Hi,
I am not able to create a Multi-Entity field for more than one Entity Type.
What I am looking for is a field like the note_links on Notes, which is Multi-Entity and Multi-Entity-Type:

What I am able to to do is this (only one type selectable):

Is there a way to enable such fields either in the Site Prefs or via support?

Best,
Tobi