I was curious about this so I checked Amazon's help page. They list footnote editing as a known issue, saying it can't be done. If they can't be edited, I assume they also can't be created. And a footnote would be the only way to theoretically create an image pop-up (assuming this means something like a "click here to view" pop-up), though to be honest I doubt that would work very well even if coded manually. Though I've never tried it, so I could certainly be wrong.
If you're curious about that help page though, it's here: https://kdp.amazon.com/en_US/help/topic/G7R2L7V5X6SJH948#known. It's sort of funny how difficult it is to search online for anything relating to KC, because searches for basically anything that include "Kindle Create" just return lots of stuff about creating things for Kindle but have nothing to do with the software itself.
That's probably just a weakness of KC. I haven't tinkered with it much but it doesn't seem tailored for more complex needs. From what I read, it kind of sounded like your best shot at it would be to build things like that out in word and then import them rather than try to create them in KC. Which is a good thing honestly, because KC does not offer a good way to extract the work you do within it as anything other than a KC file.
Maybe by doing your own CSS formatting, and not using Kindle Create at all? KC is known to be buggy and less versatile. Why anyone uses it is beyond me. Seems to be simpler to set up a Word document with Styles and go from there. Or do print on InDesign or a similar program.
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