We have many items that are related to one another, where when a particular item is being added to an order, we need to see a list of all related items that could potentially go with it to quickly add them to the order as needed.
First, when editing a particular Item, we need a way to add all of its related items, such as a multi select lookup to search for and select all of the items to show on a list.
Then, when we are creating a new Estimate, Sales Order, or Invoice, and when adding an item to the order, in the event that item has related items defined at the item level, there could be something to click to bring up the list of related items that can potentially go with that item and select any of them to add them to the order.
Best I can tell this is not currently possible, but it would make it so much quick and easier to find and add the additional items to an order.