Recently I invoiced a client using a multi-invoice template that covered 12 projects. I selected one project and, in the invoice edit window, checked Multi-Project invoice. The changed I'd like to see comes after this invoice is generated.
In my Categories & Rates preferences, I have the Auto-Update Settings set to change a project's status to "Invoice Sent". When using a Multi-Project invoice, this status is changed for the project from which the invoice originates, but not for any of the others. I think it would be more consistent if a status change was sent to all the included projects.
Further, the invoice itself is only shown in the originating project's Invoice window. If I want to review this invoice, I have to remember from which project it was generated and I think it would be helpful if each of the projects had a link to the original invoice. It might be displayed in the other projects' Invoice windows with an icon similar to a Mac's alias icon (i.e., add a small, curved arrow in the lower left).