It's good to see you here in the Community, Michele74. Allow me to share some information on where you can get the custom fields in QuickBooks Online.

You can get the custom fields if you're using the QuickBooks Online Advanced. This feature lets you track the information that matters most to you and your customers.

If you're unable to find this feature under your Lists, you might consider upgrading your plan so you can start using this option. Here's how to change your subscription:

1. Click the Gear icon ⚙ and choose Account and settings.
2. Select the Billing & Subscription in the left panel.
3. In the QuickBooks Online section, select Upgrade your plan.
4. Choose a plan and select Choose plan.
5. Hit Get started.

Once upgraded, you can take a look at the following article to know more about how custom fields work in QuickBooks: Create and edit custom fields in QuickBooks Online Advanced. This will provide you details from adding to managing your fields.

Kindly update me on how things go by adding another comment here. I want to make sure you're all set or if you have follow-up questions about the custom field feature, please let me know. I'm here if you need further guidance. Have a great day!