Select (highlight) all the clips on both tracks, using <ctrl-A> OR only those that you want to be kept in sync by holding down <ctrl> as each is clicked.
Then right-click on any one of the selected clips and GROUP CLIPS.
Now when the :20 clip is inserted into either track, the grouped clips in the other track will shift as well.
In this example ALL clips were grouped. They then could be dragged to the left - in concert.
Group.mp4