Why does Quickbooks Online limit me to 3 custom fields on Invoices

Quickbooks Online has an unfortunate limitation that only the first 3 created Custom Fields can be exposed to 3rd parties, such as Vinosmith.

If the custom field is not visible to Vinosmith then it cannot be read from or written to when Vinosmith reads/writes an Invoice.

This is not a Vinosmith limitation but a QBO one and Vinosmith has no control over this limitation.

Please see this article for more information:

https://help.developer.intuit.com/s/article/Enhanced-Custom-Fields-for-QuickBooks-Online-Advanced

Potential Workaround: use Department or Location list to track the Sales Rep.