Thank you for posting this in Microsoft Q&A.
I understand you are trying to execute a query to obtain conditional access policies in Graph Explorer with a Global Reader user, but you have received an error message "You cannot perform the requested operation, required scopes are missing in the token".
Conditional access policies can be acquired using a Global reader user through Microsoft Entra. However, in order to utilize Graph Explorer, the "Policy.Read.All" scope is necessary.
To obtain conditional access policies via Graph Explorer use below HTTP request.
GET https://graph.microsoft.com/v1.0/identity/conditionalAccess/policies
Prior to making the request, ensure that you have granted permission for the "Policy.Read.All" scope_._
For your reference: https://learn.microsoft.com/en-us/graph/api/conditionalaccessroot-list-policies?view=graph-rest-1.0&tabs=http#code-try-1
Hope this helps. Do let us know if you any further queries.
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Thanks,
Navya.