I don't think there is such a specific capability among the SMC roles, not from the PMM interface, but you could make that as an effective permission from the operating system level, if you have the right groups and permissions. Meaning: service accounts and the right interactive user accounts can read and write to the calendars folder,'s contents and the rest of users (another group) can only read the contents of that folder.
If a user can create his own flow, then he should be able to create his own calendar as well. I don't see why that has to be restricted as it would only effect his/her flow.
but users are creating duplicate custom calendars and other user are using their calendar (he thought it is created by one of the admins and that calendar was wrong).
We can tell the users not to create one. If they need one, we can create custom calendar for their team as a system calendar.
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