Hi Michael.
I just tried putting 3 stills and a video on timeline 1.
Then clicked on clip one, then held ctrl while I clicked on the video.
This highlighted both clips and then when I let go of the ctrl key both clips remained highlighted.
Then I dragged them both to timeline 2 and messed about on TL1 with the remaining clips and finally dragged the clips back from TL2 to TL1.
If you need more timelines you can create them by right clicking in the left hand vertical bar (with the lock icon in it) and selecting the "add tracks..." item.
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Terry Pratchett (Mort).