How to zoom a webcam in KDE Plasma 5 on openSUSE Tumbleweed?

I have a Schenker XMG U706 notebook which has a BisonCam NB Pro cam in it. I remember when having used Zoom (What a coincidende in naming! :) under (dual boot) Windows I could zoom in/out the video. Now that I have to use BigBlueButton in FF under Linux my face (in appx. 1 m distance) fills about 1/8 of the video display only and apparently there isn't any option to change this in this virtual classroom app. Is there a way to change the zoom level a level below the app and the browser, e.g. in webcam settings of KDE or the OS itself?