I use content libraries because I want problems to appear randomly.
Right now learners have to click submit (or save if they want to) for all problems.
If there were 100 problems they would have to click 200 times to save and submit all problems.
That is a lot of API calls and more importantly, I often get complaints that learners forget to click submit or only submit the last problem.
My suggestion is the saving action should happen automatically (save buttons are removed) and there should be an option to allow learners to submit all problems at once at the end of the timed exam.
Let me know if your users have the same issue.