CastleMania Games is now selling qwertymodo’s ‘RGBench’: A device designed to make it easy to connect component video, SCART and VGA, directly into an oscilloscope, without constantly changing cables: https://retrorgb.link/rgbench
I’ve personally tested this device and have found it to work very well for testing video voltages. It’s switchable 75ohm termination means it’ll work well both when connected directly to a scope (turn them on), or with T connectors. routing the signal to an RGB monitor (turn them off).
For more information on testing with oscilloscopes, please check out the main section and the introductory video below: https://www.retrorgb.com/oscilloscope.html