Hello @Michael Mican ,
For contacts currently there is no property to show or hide from GAL.
user resource supports showInAddressList
property, but there are some limitations with this currently known-issues.
When querying users through Microsoft Graph, the showInAddressList property may not indicate the same status shown in Microsoft Exchange. We recommend you manage this functionality directly with Microsoft Exchange through the Microsoft 365 admin center and not to use this property in Microsoft Graph.
Hope this helps.
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