Running the final 21.10.28 version, desktop.
I just found out that when you enable a custom field into the lines of invoices, and you set the field as a drop-down list, it doesn’t work a a list, but as a plaint text field.
Is this a bug?
No, not a bug. As discussed in several previous forum topics, that feature has not been fully implemented, despite sharing an entry form with regular custom fields where it has been. All line item fields function as text.