Q. Why can't I import/export 4K video?
All iOS devices that support 4K recording also support 4K editing in KineMaster.
However, 4K video used for video layers will be limited on certain devices. On such devices, you have to convert a 4K video to a lower resolution, and then add the converted video as a layer. For detail, please refer to How can I make a lower resolution copy of a video?