For the to-do lists, students can correct their own list: https://community.canvaslms.com/t5/Student-Guide/How-do-I-use-the-To-Do-list-and-sidebar-in-the-Dash... The student view of the to-do list has a little x next to every item, and they can click each one to remove it from the list as they go. There is no need to wait for the list to add up.
I'm not sure it is wise to try to delete the prior quarter grades and submissions, but there is an open idea conversation about hiding them: https://community.canvaslms.com/t5/Idea-Conversations/End-of-Quarter-Needs/idi-p/419488
In the meantime you can possibly edit the assignments at the end of a quarter to grade type "not graded." I would be careful to save a copy of the grades and feedback of the first student before you do that for, so that you can restore anything that might be deleted, just in case. If the grade and feedback and submission are all saved despite the change to no grade, then this should remove it from their, and your, gradebook.
This discussion post is outdated and has been archived. Please use the Community question forums and official documentation for the most current and accurate information.