I currently have opencart 1.5.6 and am using a paid module for back end order taking.  One screen to search for current customers or to add new customers, which leads to an order page and then payment processing.  I can also manually type in products that are not in the catalog, apply discounts, change shipping costs and taxes. 
I tried the demo of the back end for thirty bees and from the order screen it get confusing.  Is there any easy way to do this with thirty bees?  I didn't see any modules for this.   I don't want to be doing this for customers on the front end.