I WISH I could take credit for discovering this, but my colleague Staci Graff told me about this.
If you want to copy something in your course, assignment, quiz, rubric, etc, there IS a way!
Go to settings>import content>copy canvas course. Then do a search for the course you are in! It will give you a warning that importing into the same course will create a copy. Then pick "selected content" and find what you want to copy. Once it's done, you may have to figure out which is the copied version or which is the original, but for assignments and quizzes, it will be easy since they will be in a category called "imported content."
If you need to make multiple copies, make sure you make a copy of the previously imported item, or it will overwrite the first one! So for example:
I make a copy of Assignment 1. Assignment 1 will now show up twice (with the copy being in "Imported Content"). You need to update the name to something original, like... Assignment 2!!
Now when you go back to import content, make a copy of Assignment 2 and NOT Assignment 1, or else Assignment 2 will be replaced with a new copy of Assignment 1.
It's not perfect, but it WORKS! And is a great time saver!