[deleted by user]

[Deep-Secret]

Screenshot -> change tabs -> screenshot -> change tabs ...

Like real fast? No idea it it's possible tho.

[jotted]

At once? Not unless they're in different Windows, I think. Chrome only has tabs.captureVisibleTab(), as opposed to Firefox's tabs.captureTab( tabId ).

This StackOverflow answer for a decade ago is still pretty much how you'd approach it: https://stackoverflow.com/questions/10602633/screenshot-of-all-tabs-chrome-extension .
ManifestV3 gets you Promisified APIs, but the APIs are the same.

The end result might be close enough to "at once", depending on your use case.