Hello there, @ks19,
Are you referring to billable expense transactions? If so, we're currently unable to add or modify a column to add the vendor name once expenses are linked to invoices. As an option, you can use the Description field to indicate which supplier it is from.
Please refer to the screenshot below:
I understand how beneficial it is to have this option available in the program. I am submitting this feedback to our developers who implements product enhancements and features for QuickBooks Online. They are working to deliver the best tools that is essential to every customers.
You can also create a custom field for the vendor name. Here's an article to guide you how: How to add custom fields to invoices?
Please get back to me if you have other questions with QuickBooks. Leave a comment below and I'll be with you as soon as possible. Have a lovely day!