Peter wrote: Using the re-sizing cursor to make clip-4 smaller (dragging from right to left with the re-sizer) then clip-5 stays in the original position. But dragging the re-sizing cursor to make clip 3 smaller then clip 5 moves an equal amount to the left.
Normal; dragging either handle of any clip, including clip 1, will shift the timeline but not alter the gap between clips 4 and 5. When the right handle for clip 4 is dragged left, the gap increases.
Is there a way of making clip-2 stay in position when re-sizing smaller clip one to the left – i.e. leaving a gap between 1 and 2? It gets dragged with the resizing of clip 1.
First drag clip 2 slightly to the right, creating a small gap. Then the right-handle on clip one can be dragged left, to shorten that clip. To close the gap right-click in the blank space and CLOSE GAP.
Sequence 1.mp4
Having unlinked the audio from its originally linked video clip is it possible to re-link it?
Usually. Right-click | RESTORE LINKED.
Similarly with an image and a separate sound running under the image is it possible to link the sound to the image so wherever the image is placed the sound goes with it?
Try selecting the clips, then right-click and GROUP CLIPS.
It's unclear precisely what is being done in your Q4 but keep in mind that higher tracks override lower tracks. Place a clip on track 1 and another immediately above it on track 2 and only track 2 will be seen - unless its size is smaller than track 1. In that case track 1 will be in the background - picture-in-picture.