When you process an Accrual you need to Dr the Expense and Cr Accruals. Then when you pay you Dr the Accrual and Cr Bank Account/Directors Loan
With the current functionality you can only Dr and Expense and Cr a Bank Account or a Directors Loan Account, so for an accrual you are not able to attach a copy of the Supplier invoice as the Cr is never to one of the current allowable GL’s
The same applies to a Journal as with every Journal you should be attaching supporting documentation to substantiate.
Hope this helps and thanks for the quick response.