There is a known issue, where the user has created a vendor or a customer wrongly and want to delete the vendor/customer again.
If they have created financial dimensions based on vendors/customers by “using dimension values from …”, the the creation of a customer/vendor has automatically created a financial dimension value. And that prevents the user from deleting the wrong vendor/customer, even though no transactions has been made.
So in order to prevent having frustrated users/customers, I recommend, that you develop a functionality, where it is possible to delete an “unused” vendor/customer (and the corresponding financial dimension value), if the only issue when deleting is, that they have chosen to have a financial dimension based on vendors/customers.