Could it really be that simple?!

Holy shit. It really is that simple.

Thank you.

you can also use alt+enter while the cursor is inside of a multi-buffer, and it will open at that point in the file.

Even after figuring this out for myself I still struggle to do it fluently.

There's a setting that will allow you to double-click to open a file from the multibuffer which I find more natural:

  { "double_click_in_multibuffer": "open" }