If you're looking to add a custom field as a column on the bill or expense page, it isn't possible, controller16.
Please note that the custom field in QuickBooks Online (QBO) appears only at the top part of the form. For visual reference, refer to item number 1 in the screenshot provided below.

If you have a QBO Plus or Advanced subscription, you can include the Classes column once you activate it in the settings. Please refer to this article for the steps: Turn on class tracking in QuickBooks Online. Refer to item number 2 in the screenshot above to see what it will look like after activation.
You can run vendor reports to get a comprehensive overview of your accounts payable transactions.
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