How to suppress success message from custom system action


What is the problem?
I've created some custom system actions in config.yaml that call Python scripts to control my webcam to focus in/out, and increase/decrease exposure. Each of these four is its own system action, plus I have one more that does a basic initialization of the camera settings. All of these work well, but executing each results in the green "command executed successfully" message box, which is unnecessary since I have visual feedback in the control webcam window. Additionally, they tend to overlay the webcam window, making visual inspection of the adjustments difficult. I would like to suppress these messages, but can find no way to do so.

What did you already try to solve it?
I've searched within the documentation and the greater web and can't find any available option to suppress these messages.

Additional information about your setup (OctoPrint version, OctoPi version, printer, firmware, octoprint.log, serial.log or output on terminal tab, ...)
I'm running OctoPrint 1.3.10 / OctoPi 0.15.1 on a RPi 3 B.