The test tool is developed with the goal of ensuring that all students take the test under the same conditions. This means there are limits to what can be edited after someone starts taking a test.
Changes after a student has started taking a test
Question score: If you have already scored a question manually, you cannot set the new question max score to a value lower than the highest score you have given any student.
Category assigned to the question: You can only change the category score if the category does not contain manually scored questions.
Category score: If you change the category of a question, this means you could potentially change the distribution of questions for some students compared to your setup for when drawing from categories, if their selection contained the question that is changed.
When you save changes that affect the calculation of score, attempts that are already submitted will be recalculated. You will see a notification that this will happen, and need to confirm your action. This can only be undone by manually changing the score back to what it was before.
Deadline: Can only be changed to a future date
Number of attempts: Can only be increased, not decreased