It's good to see you here in the Community, @Peterb2.
The option to enter ABN on the work info page is currently unavailable in QuickBooks Self-Employed (QBSE). As a workaround, you can enter your ABN on the description field when creating an invoice.
I can see how helpful for you and your business to have this option on your invoice. For now, I suggest submitting feedback directly to our product engineers. This way, they can look into this option further and consider adding it in the future update. To send feedback, you can go to the Invoices page and select Feedback.
You can also visit our blog site so you'll be able to get the latest news about QuickBooks and what our Product Care Team is working on.
Please continue to reach me here in the Community if you need more assistance creating invoices. I'll be sure to get back to you.
Thank you for your valuable feedback on how the Edit work info option looks on an invoice in QuickBooks Self-Employed. Know that we recognize that each company has unique needs, and I can see how this option would benefit your business.
Feel free to send you feedback or product suggestion by clicking on Assistant tab in the top right and type Feedback.
Please let us know if you need any help. Have a great day.