unfortunately, I'm not finding any answer to your question - usually, every known Google Analytics limit can be found in , but not this one.
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Well I still have not found the answer to "Shortcuts" but it appears that "Custom Reports" has a limit of 100 reports. I will use this instead of shortcuts because I can still reference them in the Dashboards and "share" them. Shortcuts are not shareable at this point so it seems like custom reports is the answer.
BTW - Here is another good Google Analytics limits cheat sheet. https://www.cheatography.com/dmitry-klymenko/cheat-sheets/google-analytics-limits-and-quotas/