Large JPG images in Movie Edit Pro Plus 2022 need brightness and saturation to be substantially increased for the video file to look like the originals. Is this right, please, or is there a setting I have missed?
No, personally I can't say I have. I have seen people have odd problems with jpgs that have a 444 chroma colour sub-sample as ideally they should have a normal 422 chroma sub-sample. I don't think it is that in this case though.
Beyond that I can't think of anything or a setting you may have missed. Videos in general do not have the full 0 to 225 colour range you may see in a jpg on screen and tend to be 16-255 unless an individual sets it otherwise, but I'm not sure most people would notice and should only effect the shadow areas. Are you using a 4K monitor? If so you may have to enable HDR settings for video in windows.