I use a dummy 3rd screen, where I put the dmd on. With dndext I mirror that one to my realDmd. I didnt like that the dmd didn't show anything in attract mode. Its not ideal, but like it this way.
And totally agree with @joyrider3774. My recommendation would be: Skip pinball arcade and use vpx or zenfx3 (not sure if it was still on winter sale, but good price on steam last month)