This is an old thread, and there may be another one that answers this question but I have not seen it. I am running into the same issue, based on the description that @AliciaSwackhame gave.
We have the ability to create rubrics at the account level , which are not associated with any courses. Similar to the way we are allowed to create Outcomes at the account level.
Unlike Outcomes, which can be accessed from the courses in the account and subaccounts, the rubrics are not accessible from courses in the account, at least not that I have found. I have tried creating a new rubric, which only allows importing a file, I have tried searching for one but (as I expected) that only searches the existing rubrics in the course, I tried building a new rubric associated with an assessment but was only able to access the account-level outcomes and NOT the rubric that was already created at the account level.
According to the Guides, we have the ability to do this, but none of the Guides seem to be demonstrating accessing a rubric that has been created at the account level, outside of a course, despite the fact that we clearly have the ability to make rubrics in that location.
I know I have to be missing a very simple key element, but have yet to find it.