how do I select 2 docs in Binder → Split Vertically (ie display side by side vertically)

Scr3 ver 3, Catalina latest update
If I Cmd-Click on 2 docs in the binder → View → Editor Layout → Split Vertically : I see the same document (one of the 2 chosen in the binder) displayed twice side by side in the split editor.
I can’t figure out how to select (Cmd-Click) 2 docs in the Binder → display the selected docs side by side vertically, with as few shortcuts as possible.
thanks in advance for your time and help

The trick isn’t to select both of them at once, but rather to select one after the other, one for each split:

  1. Click on the first document. Now it is loaded.
  2. Opt-click on the second document: it loads in the other split, creating one if necessary.

Be aware of the Navigate → Binder Selection Affects menu, which defines what happens to which half when you click in the Binder.

Katherine

thank you !