If you're not using Xero Expenses, you can submit expenses as Xero Bills with these workarounds:
Submit each receipt as a Xero Bill instead of adding all of them to one Expense Report. This works perfectly well if you only have a few reimbursable expenses.
Use a 3rd-party tool to submit expenses:
Dext can process expenses and publish Expense Claims to Xero as Bills.
Or, use any other OCR tool that can publish expenses as Bills to Xero.
Use a dedicated expense tool like Expensify.
Use employee debit cards to pay expenses (Pleo, Expend, Soldo). Such tools capture the receipts and publish the transactions to Xero.
Create Bills in ApprovalMax as this article suggests.
Use ApprovalMax Capture to recognise expense receipts and automatically create Bills from them in ApprovalMax. You can use the ApprovalMax Pay add-on to pay such Bills directly from ApprovalMax.