New Order Store - System Option

X>Utilities>System Options>Order Entry>Order Entry 

Category-Default Values

Type- Can be Global, Assigned or User

Use this option to select the default store code for orders created by a certain user.

This is very helpful when a users enters orders for multiple stores.

Default store: Select this for the store code to be the same as the default store code associated with the user.

Customer Store: Select this for the store code to be the same as the default store code associated with the customer record.

None:  With this the user will have to select a store each time.