I'm sharing more information about switching your vendor to contractor list, @nellpark.
Currently, QuickBooks Online cannot switch your vendor to a contractor. However, we can manually add your vendor name to the contractor. Here's how:
On the left panel, click Expenses.
Select Contractors.
On the right side, choose Add a Contractor.
Provide your contractor's name and email.
Hit Add Contractor.
Please note that you need to ensure changing or adding an initial to your contractor's name, as QBO will not allow a duplicate name. If you want to track your vendor's 1099 instead, follow these steps:
Go to Vendors, and then click the vendor name.
On the upper right, select Edit.
Under Additional Info, check the box for Track payments for 1099.