If the workflow for a document related to D365 Finance project management and accounting module (e.g., project invoice proposal) turns into "Unrecoverable", users cannot cancel/edit/delete/resubmit the document. There should be a provision to perform such actions. 

Microsoft have introduced features for that purpose for documents related to accounts payable, accounts receivable (free text invoices) or general ledger (journals). However, there is no solution/feature provided for project management and accounting module.