If your Vendor uses mostly the same distribution each time you pay them, you may set up a default Account Distribution in the Vendor's Record.
You may use a percent distribution method or a dollar amount method. To delete a distribution simply click on the red X next to the line you want to delete and click SUBMIT.
When you select the Vendor in the Bill's screen, you may choose to use the distribution or not.
Even if you choose the distribution, you can remove any unwanted, or update each one to the pertinent Account Codes and Amounts.