Apple says: "If something people do within a sheet results in another sheet appearing, close the first sheet before displaying the new one. If necessary, you can display the first sheet again after people dismiss the second one."
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To me, closing the first sheet before displaying the new one, and then bringing back the first sheet, seems like a more confusing and unnecessarily complex interaction...
I agree. I think it’s on the software to make the organization of content clear; it’s not a fundamental problem of sheets, it’s simply often a poorly executed design. It’s an information architecture issue that requires careful application of interaction norms.
While adding a widget you can watch the beauty of sheet in a sheet. No damage caused.