Add view with only dimensions from other views

I have an explore with 3 views
view dimension
A page.id
B event_loaded
C event_loaded

I want to make another view that only contains dimensions of B and C combined and then join them into the model so i can give it a separate view label.

view: all_events {
  # To add combination of A and B dimensions to the explore.
  dimension: is_loaded {
    type: yesno
    sql: ${A.event_loaded} OR ${B.event_loaded} ;;
  }

Explore:
….
  join: all_events {
    from: all_events
    type: left_outer
    relationship: many_to_one
   sql_on: 1=1
  }

The only issue is that I miss a join key.
I thought I read --somewhere-- that i could do the above, but it doesn’t work.
Any idea’s?