In one instance of OBS? No.
But you can use the -multi command line switch to open two copies of OBS. Be aware this will encode the video twice, and increase your CPU usage. Generally you want to use two Profiles, and control the scene switches with hotkeys so both OBSes change together.
I'd actually say that 20mbps is pretty low, for 1440p@30.
Also, unless you are a Twitch Partner, 3500kbps is strongly not advised; non-partners should aim for a 2000kbps maximum streaming bitrate.