Hello there, Gene. Allow me to provide details about the attachment feature within the QuickBooks Self-Employed (QBSE) program.
The option to add attachments in QBSE isn't currently available. You're right that you can only do it in QuickBooks Online (QBO). That said, you'll want to upgrade your subscription to QBO to utilize this feature. Here's an article for more details about the process: Switch from QuickBooks Self-Employed to QuickBooks Online.
Additionally, kindly visit this resource for information on how QBSE tracks your business income and taxes: QuickBooks Self-Employed Overview.
I'll be here to share other details with you if you have further questions about managing attachments. Kindly add them to your reply and I'll be sure to provide the necessary assistance.