As far as I know,there is no way to confirm whether the user has viewed an item.
As a workaround, you could save the user information to a list when the user go to the display form of a list(whether it’s automatically executed code or insert a button to let them click to confirm that they have viewed this item).
Or you could submit a feedback to UserVoice.If a feedback is high voted there by other customers, it will be promising that Microsoft Product Team will take it into consideration when designing the next version in the future.
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