You want to delete multiple Ad hoc reports or ORD Queries/Reports from UI.
With the current functionality it's only possible to delete one at a time.
This is considered an enhancement request and already been submitted. https://influence.sap.com/sap/ino/#/idea/201315/
From the UI one can't delete multiple Adhoc report at a time but only one report at a time. This is considered an enhancement request and already submitted https://influence.sap.com/sap/ino/#/idea/201315/
Delete Adhoc report Adhoc report deletion , KBA , LOD-SF-ANA-ADH , Adhoc Reports & Report Builder , Problem