Ideas

In the example screenshot, I can't click 'Relate Selected Items' because I haven't set a Relationship to the Organisation (top right corner.)

Perhaps allowing a default to be set, or making the Relationship field more obvious on the GUI?

I've had a couple of times where our analysts have asked me why they are unable to attach a user to an organisation and the answer is because they have missed this field. Either having it default to 'Employee'/something else, or some sort of "look over here" would avoid confusion and frustration.