Ability to move invoices to a certain project!

Now that we can create invoices without first making a project, I’d love if we can move the invoices to the project once we’ve created it. I usually charge for my initial consultation (thereby creating an single unattached invoice) and would love to be able to stick that into the new project. Same with questionnaires. There are times I have found it would be handy if a completed questionaire can be moved to a project. Thanks!