It's fairly easy to copy grading schemes from one Canvas course to another. Here's how:
Go the the course in which you want to import a grading scheme.
Click on Settings in the course menu.
Click on Import Course Content, located on the right side of the page.
Select Content Type: Copy a Canvas Course.
Search for a course name of the course from which you want to copy the grading scheme.
For Content, choose Select specific content.
Once you've clicked Import, you'll see a Blue Select Content button appear. Click it.
On the next page/screen, click the checkbox next to Course Settings.
Then click the Select Content button (again), located at the bottom right of the screen.
Once the copy is completed, a green Completed button appears, and the grading schemes will be copied.