With custom fields, you can only map one field to another.
Can I use a conditional to map a custom field?
There is no conditional saying if the shipping method was UPS, then map tracking as UPS tracking. As a workaround, you can map a field that has no mapping to QuickBooks. Then, map that field to the custom field.
How do I add a rule to map a field?
In this example, we will use the field called order other. If you click the formatting tab in QuickBooks and click customize data layout, ensure the other field is unused. If it is used, you could also use project, FOB, or check number.
Next, let's hard code a value: