Is it possible for Moodle to speed up manually adding and deleting reviewers and reviewees. It is incredibly slow to deal with this one at a time, with changes back and forth across screens, for every single change. Click, change of screen to verify, veryify, change back to previous screen. This seems to be a problem across Moodle. Moving, adding or deleting outcomes to assignments is even worse, including going back to the beginning location in the original screen, requiring nauseating scrolling across the gradebook or view in Outcomes.
I don't think it is at the moment.
The manual allocator has been implemented primarily for the use case when a teacher needs to assign/revoke just a couple of allocations manually. It was expected that the random allocation method should be used in most cases. I can understand it's far away from being optimal when used for assigning more than a few allocations.