@SusanNiemeyer ...
Ugh...I can see how frustrating that could be...and yes, an auto-save feature would be handy.
Out of curiosity (and this might not be a real solution to your question), have you ever tried using @James' "Canvancement" (Canvas Enhancement) to import a rubric from a spreadsheet? I used it all the time in my past position as a Canvas administrator, and it was awesome! Saved me tons of time!
I'd be happy to help if you were interested in trying this out or if you have questions about how I used it when I built rubrics for courses I worked on.
I did find this past Feature Idea which has been developed, but I *think* it only applies to brand new manually created rubrics that might not have been yet saved...not to existing rubrics that you are just updating??? Not really sure. Assignment Rubric auto-save - Instructure Community (canvaslms.com)
As you may have seen, Feature Ideas are temporarily locked down until early February so the Community Team can do some re-org and clean-up of the Feature Idea process. This includes creating new Feature Ideas, rating them with stars, and commenting on existing Feature Ideas. Here's more info: Idea Conversations: The Path Forward - Instructure Community (canvaslms.com).
Hope this helps some.
^ Chris