Yes, that's what I want the link to carry. A and B can be the comparison labels, but I'd keep the part identity and the particular setup behind each image. I'm leaning towards a short trial note that points to the originals rather than pasting pictures into two separate documents.

I'd put the unsuccessful comparisons in that trial note too, even if the gallery only needs the clearest examples. Otherwise whoever costs the idea later sees the selected images and misses the work it took to get them. No need to make every image a whole report.

Could the index show missing captures too? No image and an unhelpful image are different problems.

Yes, fair distinction. I'd want a row for an intended capture even if there's no file, with the reason left unknown if we don't know it. A dark image at least gives me something to investigate (not necessarily a camera fault).

Exactly, and don't turn that missing capture into an inspection pass or fail when somebody totals the sheet. It belongs in the account of the trial, but you haven't got an inspection result for it.

There's another case I want the note to allow for: an attempt stopped before a capture was due. I wouldn't want that quietly merged with 'capture expected, file missing'. Same empty thumbnail, different question to investigate.