Did you ever see any progress in this? I'm running into a similar situation. Our external tool doesn't define max value for grades
This is an old post, but I have the same situation and can't find a solution now either. Any new ideas?
I have the same problem with the external tool Atomic Learning. There doesn't seem to be a way to set a grade other than 100. Any help with this would be most appreciated.
I submitted this to the tracker. If you agree this should be addressed you can vote for it here:
https://tracker.moodle.org/browse/MDL-49161
This is a major hurdle for our institution. With the large adoption of LTI of vendors the inability for Moodle to adapt easily (or at all) is amazingly cumbersome.