Hi @ArunKumar Arumugam ,
Unfortunately, this is not possible using SharePoint Online JSON formatting or Permission Level to hide "Details" option from SharePoint mordern list.
SharePoint Online command bar JSON formatting only supports the keys available in Microsoft official documentation at: Command bar customization syntax reference - key
As a workaround, ”Details“ are available in the modern SharePoint interface, but you can hide ”Details“ option by Return to the “classic” SharePoint.
Hope the information can help you.
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