In SharePoint Online, in the Content Type Gallery, I un-checked "Show this column in lists" for the Recurrence column in the Event content type. Now, when I re-check it, the "Save" button is still disabled, and now the recurrence field is not visible on calendars, and there seems to be no way to get it back.
My question is, is there any way to re-show/re-enable the recurrence columns' visibility for the Event content type?
I have reproduced this issue on my account. It seems that it could work normally when we change the option between "Optional" and "Required". However, when we uncheck "show this column in list", we could not change it back any more, the site column will always be hidden.
We could only create a new site column. What's more, we will not get an error even if we use a same name, it seems like the previous column has been deleted from site columns.
You could send feedback to Microsoft SharePoint Feedback so that it could be improved one day.
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