At first I couldn't get the work-around as explained in the video and other comments above to work with RX6 in Studio One 3, but by following these steps I got it to work!
1) Select the audio clip you want to edit.
2) With the Inspector Panel open, Drag the RX6 Monitor to the track Inserts.
3) Click "Enable" on the track Event FX. Drag the RX6 Connect to the Event FX.
4) Open RX6 standalone, go to Edit --> Preferences, and update the driver type and output device to "RX Monitor".
5) Click "Render" on the Event FX. Double click and open the RX6 Monitor and it should now say "Connected".
6) After editing, saving, and replacing the audio clip I had to turn off the RX6 Monitor for my audio to work again in my DAW.