You'll want to add this supplier as a customer, cabocraft.
Since QuickBooks Online doesn't allow two identical names, you can add a character or maybe a middle name for this customer.
That's it! You're now able to add this supplier as a customer.
If you got questions about the process, just leave a reply below.
Thank you for joining in the Community forum, @amar01.
Currently, you can only merge duplicates of the same type in QuickBooks Online. You can merge a customer with another customer, but there isn't a way to merge a customer to a supplier.
However, you have the option to merge two accounts depending on its type. You can refer to this article for more details: How to merge accounts, customers, and suppliers.
Please know that the merging process is permanent and can't be undone at a later point. If you have follow-up questions regarding this process, do let me know. I'm here to help.