Yes, well sort of. I just discovered a way by a long bit of googling, but it's not perfect, and you can't see the cursor on this "secondary display". You have to download Splashtop Client on your computer (Windows 10) and then the splashtop app on the surface rt (from the microsoft store). You can use it to remote desktop your computer screen from the surface which by itself is very useful. Then you have to use a driver that tricks windows into thinking it has a secondary monitor connected when it really doesn't. This used to be something you could do in windows 8.1 and windows 10 but now it's patched for windows 10. Here is a link to a company that made a driver that is working for me to "create" a fake secondary monitor: https://www.amyuni.com/forum/viewtopic.php?t=3030
Go to your display settings on your computer after using the driver and you should see a second monitor detected. Click on the dropbox to select "extend these displays".
After doing that, just connect to your computer from the surface rt on splashtop, then click on switch display on the bottom taskbar to see the extended desktop, and boom a semi-usable secondary monitor.
Unfortunately you can't see the host computer's cursor on the surface display (please help me figure out how!), but other than that, it seems to work as a good 30fps secondary monitor if you have a good wifi connection. Usable enough for videos imo.
