Thanks for getting back to us, @Rescale.

I appreciate you for following the steps shared by my colleagues above and providing a screenshot of your concern. Allow me to chime and share additional details, so you can see the Custom field section.

You can see the Custom field button when enabling it in the All lists section. From there, you can add your custom fields. Let me show you how.

1. Go to the Gear icon.
2. Under Lists choose All Lists.
3. From the Lists, menu select Custom Fields.
4. Click the Add custom field and enter the necessary details.
5. Once done, tap Save.

For detailed steps, you can check out this article: Add and create custom fields in QuickBooks.

If the issue persists, I would suggest contacting our Customer Support Team. They have available resources to look into your account and can further investigate this. Just follow the steps in this article on how to reach them: QuickBooks Online Support.

I'm adding these articles that will help you manage your custom fields and track the details that matter to most of you: 

• Filter, search, and sort with custom fields
• Use custom fields in reports in QuickBooks Online Advanced
• Use custom fields for vendors and expenses in QuickBooks Online Advanced

Please let me know in the comment section below if you have any other issues or concerns. I'm more than willing to help. Have a wonderful rest of the day!