Hi there, @mangokh.
Thank you for reaching out to us here in the Community. Allow me to share some information about importing products to QuickBooks Online (QBO).
We can import products and services from an excel file to QuickBooks. However, as of now, we don't have the option to import the preferred vendor when importing products and services.
I'll take this as feedback and submit it to our product engineers. Please note the feature implementation varies on the number of customers requesting it.
You can look for an app that can help you import the preferred vendor in QuickBooks Apps. There you can look/enter the service available in an app in the search box like export and import.
Also, to learn more about new features being added every month, you can check out our blog at: https://quickbooks.intuit.com/blog/whats-new/.
To know more about importing products and services, please check this: Import products and services.
Please let me know if I can be of additional assistance or should you have any follow up questions. I’ll be here to help. Have a good one!