Hi @StephenWalsh ,
I think this feature is confusing because you don't use the View/Edit button to edit. Instead you want to click on Manage All Grading Schemes below that. This guide describes the edit process near the bottom under Manage Grading Schemes.
How do I view grading schemes in a course?
If you already are in this area and it's grayed out, then your institution may have disabled the option. The very bottom of the guide describes other reasons you may not be able to edit a grading scheme.
