Thank you for posting here in the Community, @cheryl30.
I can see how the workflow you're looking for is beneficial to your business. Right now, this feature is still unavailable in the Self-Employed version.
Right now, the only option available is to save the invoice as a draft and get back to it later on whenever you're ready (see sample screenshots below for your visual guidance).


If estimates are required, I suggest upgrading your service to the QuickBooks Online version.
For future reference about the set up when you upgrade, visit the Set up and use estimates article. It provides everything you need to know with the feature.
Stay in touch whenever you have additional questions about QBSE. I’m here to make sure you’re taken care of. Have a great rest of the day.