Hi @Jacob Margolis ,
It seems that you are using new Outlook 365 desktop client version so "Permission Level" setting doesn't existed in new version.
That's the expected behavior now. If you want "custom" levels, use PowerShell. Or use a reg key to bring back the old dialog: Restore Outlook's Classic Permissions Dialog
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Besides, as a workaround, go to OWA, Under Calendars, right-click the calendar you want to update sharing settings for, and select Sharing and permissions.
When other people open the shared calendar in outlook, they can see all views include categories like the screenshot
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