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.

Click Import.

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.