Moodle 3.5
When changing points for questions manually there is a function documented to recalculate the grades for several attempts at once. It is supposed to be found in the overview of attempts within the quiz. I cannot find any option like that. There is a bug though, that only the "detailed" option will list students and attempts, while the regular list shows a database error. Is the function maybe only to be found in the regular list?
I am not sure if this is exactly what you are looking for. For a "Quiz" you can click on the attempts, and then see the Regrade options under Display options.
I am pretty sure by now that this is related to: https://moodle.org/mod/forum/discuss.php?d=384732
These options are probably there, but since there are no results from the database, the options what I could do with selected entries from the list don't appear...
I was right, with the solved bug as seen here https://moodle.org/mod/forum/discuss.php?d=384732 the manual grading is now possible