Unable to add a star item directly on a sales order line

Summary

We have the need to add a star item directly on the SO line for regular sales orders and returns. However system is not allowing us to add the same

Content

We have the need to add a star item directly on the SO line for regular sales orders and returns. However system is not allowing us to add the same. Is this functionality supported fr

a. regular sales orders

b. RMA

c. using order import webservices