When posting a deposit, someone has inadvertently added a payment method. So, how can I edit (delete an incorrectly added) payment method from the drop down menu?

I can help you with the payment methods concern, kimmie99. 

Updating or making them inactive is quick and easy. Let me walk you through the process.

1. Go to the Settings icon in the upper right corner.
2. Select All Lists.
3. Choose Payment Methods.
4. Click on the dropdown arrow under the Action column.
5. Select either Edit or Make inactive.
6. Tap Save.
    

You can also check some Resource Guides and tutorials to help your way around QuickBooks:

•  Record and make bank deposits in QuickBooks Online.
• Video tutorials for QBO

Keep me posted if you need further assistance managing the payment method or anything else about the program. I'll be right here if you need anything else. Have a lovely day!