Manual testing is time consuming. Anywhere between 3-8 hours per page depending on the complexity of the page and its components. If a tester is not able to complete every step in the Manual Testing Wizard in one sitting, it would be helpful to be able to mark what steps have been completed so that it is easy to pick back up where they last left off.
Expanding on the idea, a client would like to see three options available: (1) marking a test step complete, (2) marking a test step as "not applicable" because, for example, there may not be any images on the page, and (3) not yet tested.
The feedback from this client aligns with other client feedback where they would like AMP to be a system of record for not just what has failed, but also for what has passed. Clients are seeking a record to which they can point to confirm that testing has been conducted. They want testers to "attest" to the fact they have conducted each test, as applicable, on a page.