Pixel Piece Script GUI Hack AUTOFATTORIA ...
Ack, ok, I see the problem now. The metadata appears to be locked in 0.2.0m2, which I think you are using. I tested the script the other day in 0.1.3. So that will only be an option in either an earlier version of QuPath, or a later one (once the GUI allows you to edit the values directly). Regardless, you should be able to set the pixel size in FIJI through a macro. Here is where you would edit things manually, and you can use Record to make a quick script.
Pixel Piece Script GUI Hack | AUTOFATTORIA | ...
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