Issue with Custom Areas for Capture

Im trying to capture a custom area of an extended desktop, while I can select a customisable area on the main desktop or can select the entire extended desktop or specific program windows, custom area seems available only on the main desktop? Its a modular synth emulator with visual modules that Im trying to capture the output of into OBS/ Magic Visuals. Thanks. for any assistance!

I have found the same issue when using multiple monitors. My work around is to temporarily move ManyCam “main screen” to the other monitor and select the custom area. Then move ManyCam back to the original monitor. I’ve only done this once or twice but as I recall it worked; just a little cumbersome to do.