SUMMARY STEPS TO REPRODUCE 1. mark all tracks of timeline via mouse drag and add "content of timeline" to library which produces a *.mlt file in library 2. import .mlt file from library into a NEW projekt clip window 3. insert .mlt clip into NEW project and enpand marked clip. In project window only video tracks will be expanded and visible but no sound although the clip contains sound as you can hear when opening clip in clip window. OBSERVED RESULT EXPECTED RESULT SOFTWARE/OS VERSIONS Windows: macOS: Linux/KDE Plasma: (available in About System) KDE Plasma Version: KDE Frameworks Version: Qt Version: ADDITIONAL INFORMATION
The audio should be expended out of the MLT library but only 1 track (https://invent.kde.org/multimedia/kdenlive/-/issues/300#note_194770). Please try with the AppImage to check if Flatpak has a packaging issue.