Using Magix Movie Studio 2023 or Movie Edit Pro, here is how to get all audio channels of a multichannel Video file onto the timeline. The program allows you to have one of the audio channels at a time. To get both (or all) you need to do either an export/import wave file for each audio track, or the more simple mixdown of each channel to get wave files of each channel directly onto the timeline.
0:33 Case 1 - One object on timeline, Audio/Video on one track
1:58 Case 2 - One object on timeline, Audio/Video on separate tracks
3:36 Case 3 - Multiple objects on timeline, Audio/Video on separate tracks - Isolate target