I think, we speak about different things

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Try this:
- in the panel for Pages Thumbnails select pages 1-5
- in the main panel scroll down to page 6
- press del
-> the pages are deleted and in the main panel you see page 11 of the original document = new page 6
I would expect to see page 6 of the original document, which is the new page 1.
If you don't do anything else you can jump back with Alt-Left, but not, if you made some comments before deleting the pages.
I didn't say anything about expanding the thumbnails to full size.
No, but I have to read the text or at least parts of the text and that's quite difficult in a smaller view

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An explanation, why I do it this way:
I have documents with lots of pages, from which I only need a few. To know which to keep I have to read them (at least superficially). In the same time I make some highlighting. If I detect a page which I don't need, I select it in the left panel. I continue reading until I find the next interesting text. Now I mark the previous page with Shift-Click and delete all selected pages. For me that's by far the fastest method to shrink my documents to a readable length and mark all useful information.
eva