The option to add a customer with the same name as a vendor isn't available in QuickBooks Online (QBO).
However, you can add special characters or punctuation marks on the customer's name. This way, you can use the same name as your vendor.
As a workaround, you can add an indication, so QuickBooks will think that they are two different entries. For example:
JohnC - you add C at the end of the customer's name.
JohnV - you add V at the end of the vendor's name.
QuickBooks will only allow you to save it as long as you'll add one character that is different between customers and vendors.
Additionally, you can run the Customer Contact List report in QBO. This will show the list of customer info such as phone number, email, and billing address. Just go to Reports and open the Customer Contact List report.
Also, you can visit our blog site so you'll be able to get the latest news about QuickBooks and what our Product Care Team is working on.
Just tag my name in the comment section if you have any other concerns or questions. I'll get back to you as soon as I can. Stay safe.