It doesn't work - new image tab is opened every time Enter is used, if option "browser > fullscreen > viewer" is used for Enter. To reproduce go to image A in browser, press Enter 3 times, then select image B, press Enter again - image is opened in new tab.

Another Enter issue, using the same setting:
When using Enter to open image in fullscreen and then to viewer, sometimes the same image in viewer instead of actual. I can't reproduce this one yet.