New functionality that allows you to easily add companion items to a sales order will be included in Dynamics GP 2013. This will allow you to better serve your customers.
The functionality allows you to set up one or more suggested items for any given item in your item list. This means that when an item is added to a sales order, the system will pop up a new screen that shows the “Suggested Items”. You can select one or more of the items to be easily added to the sales order.
This is the screen used to identify the suggested items. This looks very much like the screen from which you can select the suggested items in Sales Order Entry:
This is a short PowerPoint deck from Microsoft, GP2013 Relate-Link Items for Suggested Sales that explains the feature.
I made this quick video to show it in action.