Kdenlive/Manual/Timeline/Grouping
Grouping
Grouping clips allows you to lock clips together so that you can move them as a group and still retain their positions relative to each element in the group.
You can select multiple clips in preperation for grouping them by holding shift and clicking the mouse and dragging in the timeline.
To group the selected clips select Timeline > Group Clips or Right Click the selected clips and choose Group Clips.
Grouping is also usefull if you have a seperate Audio and video track and need cut and splice both tracks at exactly the same point (eg for audio sync reasons).
If you cut the video clip using the Razor Tool when there is an audio clip grouped to it then Kdenlive cuts the audio clip at the same point automatically.
>> 
FAQ elements to integrate:
Q: How to delete sound track only ?
A: Right-click on track, choose split audio, The audio will move to an audio track but be grouped with the video track.
Right click again and choose ungroup clips.
Then you can delete the audio only track.
Alternatively you can keep the audio in the clip and use the Audio Correction >Mute effect to just mute the soundtrack on the clip