It's nice to have you here in our forum, @Glang,
I can share some workarounds to help you manage your lists in QuickBooks Online.
There are a few ways to correct duplicate names in QuickBooks Online. Here are some options you can try:
Merge names under the same account:
Please know that this process cannot be reversed and is permanent. For additional insight about this process, such as how data is retained, please see the following article: How to Merge Accounts, Customers, and Vendors.
Inactive a vendor or customer:
I've included some articles to guide you with the steps:
As always, I'm just a quick post away if I can be of additional assistance. Have a wonderful day!