In some overview screens you are able to multi delete lines.  The ability to does this is usually dependent on whether the item(s) have been used elsewhere within the system.

e.g. when trying to delete the supplier for purchase part record checks are made to see if the part is on an purchase requisition and you are prompted to confirm whether you still wish to delete the part even though it is on an active requisition.

However, if adjacent price objects exist then deletion isn’t allowed.

You would have to make sure that the Supplier Purchase Part hasn’t been used anywhere else or have things like adjacent price objects.  

If they haven’t been used then I would believe that you could highlight and RMB delete.

On other occasions I have gone to the overview screens to delete or write a PL/SQL to delete the items by using a cursor to locate required records for deletion then utilizing the relevant API package and the function e.g.  PURCHASE_PART_SUPPLIER_API.REMOVE__ etc.,  However, you would have to carry out the checks as part of the routine PURCHASE_PART_SUPPLIER_API.CHECK__ as this would be the part that carries out the requisite checks to confirm whether the part has any linked items.

Sorry I couldn’t be more helpful.