Google analytics - First Page of First Session Dimension

Question

It should be so simple, that it is frustrating. There is the famous 'landing page' dimension. However, a 'landing page' is defined as the FIRST page of some session. What dimension shows the FIRST page of the FIRST session of a user? For example, when I create a report, that shows for every custom event (==goal/conversion) the landing_page, I see the landing page of the session in which the event was sent. But I want to see the data (landing page, source, referral) of the FIRST session. This is also called First Touch attribution. But I can't find a way to change it. I should be simple, and I can't find any information about it.