I'd want to share some information to assist you in removing your inactive customers, @Mudu.
To delete inactive customers in QuickBooks Desktop, ensure the customer isn't associated with any transactions. To achieve that, follow the steps below.
Go to the Customers menu, then Customer Center.
Right-click on the inactive customer.
Select Delete customer job, then click Okay to confirm.
If there are associated transactions, QuickBooks will only hide them. You can consider moving those transactions to another customer or delete them if this won't impact your financial records. Refer to the sample screenshot below:
If you want to run different types of reports, you can check this article to guide you further: Create and manage reports.
Let us know if you have other queries about managing the customer list. I'm always around to help. Have a nice day.