I want to make proposals and invoices for one-off clients without saving them to my client list.

Some of my clients are one-offs. I'll do a quick small project for them, send them an invoice, get it paid, and they're gone from my life. I don't want to clutter my client list with them. In fact, they can clutter my reporting. I already know we're not going to work together again.

I want to make proposals and invoices for one-off clients without being required to save them to my client list.