When I click the Display this folder in the other file display button a copy of the current tab is opened in the other display. Is there a way to make this happen in a new tab rather than overlaying the rightmost existing tab?
As nudel says you can create a new button on a toolbar to do this but the button you're talking about in the File Display Border cannot be changed afaik.
Perhaps it should have an option to open a new tab. The button has behaved like that since before Opus had folder tabs.
BTW, if you find you're using your new button/hotkey and no longer use the one in the file display border, you can turn off the unused button. (If you don't mind turning off the Copy button as well.)