Hello,
The concept of a lead is that the person or company is not a customer yet so it does not make any sense to be required to create him as a customer in order to save the quotation.
In fact, when in the lead editor, I click on the plus sign near the quotation link, the quotation editor opens with the name of the customer as a read only field below the customer combobox, however, quotation cannot be saved when no customer is selected in the combobox, so I am forced to create him as a customer first.
I think it should be fixed. These are the software versions.
ERPNext: v11.1.19 (master)
Frappe Framework: v11.1.20 (master)
Regards
Jaime