Literature and Latte

When working in a QuickReference panel, is it possible to have its Comments/Footnotes pane shown on the right margin (rather than at the bottom of the screen)?

It is possible – with Scrivener 3!

Since DyCham said it was possible in S3, I had to figure out how.
In the QuickReference panel, select the dropdown that defaults to 'Editor' and choose the 'Comments/Footnotes' option.
When you do the Comments are displayed below the Editor pane in the QuickReference panel.

But just to the right of that dropdown, a symbol representing the option to change the split appears. Click that symbol representing a vertical split and you'll have the QuickReference panel configuration you were looking for (I think).