If we select the dynamic entry for locators then we can directly create the locators while do any transactions. To allow dynamic entery allowed for locators we need to do following two setups.
1. Make the stock locator as dynamic entery either at oraganization parameter or subinventory or at item level.

2. Allow dynamic insert should be enabled for the stock locator structure.

 
 

Now when we do a transaction we can put a predefined stock locator or can a new combination if required.