I am currently using standard 8-bit UHD video files, but am considering buying a Panasonic GH5 for the extra post flexibility of 10-bit material. I downloaded a sample video clip to try out, which shows up on the Kdenlive timeline, but when displaying the RGB parade it only shows the usual 0-255 levels. Does this mean Kdenlive does not recognise more than 8-bit colour depth video?

This is not direct Kdenlive this is MLT the video processor below Kdenlive. And MLT, as far as I know, works with 8bit only.