Thank you for reaching out to QuickBooks Community. In QuickBooks Online Advanced (QBO Advanced), to add custom fields and make them appear in the workflow condition list, you need to create and configure these fields properly.
Here's how to do it:
In the upper right of your screen, navigate to Settings ⚙ and choose Custom fields.
Click on Add field.
Enter a name for the field in the Name box.
From the Data type ▼ dropdown, select the type of custom field you want to create.
Choose the category for the field, such as Customer, Transaction, Vendor, or Project.
Under Select forms, check the box next to the form(s) where you want the custom field to appear.
(Optional) If you want the custom field to be visible on printed and delivered forms, enable the option for Print on form. Otherwise, the field will only be visible within QuickBooks Online.
Click Save to finalize your custom field.
Now that we've created custom fields, we can use them in workflow conditions. You can refer to this article for a step-by-step guide on creating a custom workflow condition list: Create a custom workflow.
If the custom field does not show up in the workflow condition list after completing these steps, verify that the field has been saved properly and is assigned to the correct type of transaction associated with your workflow.
If you have additional questions, feel free to reply to this thread.