Is there a way to submit meal receipts instead of doing per diem for grants and research funds that REQUIRE meal receipts and NOT per diem?

Yes.  Accept full per diem and then reduce the per diem to what the meal receipts total is by using the miscellaneous expense type. Enter Vendor Name as ‘Reduce Per Diem’ and put a negative amount to reduce reimbursement. Because it is a credit, there is no need to attach a receipt.