In some cases, it might be helpful to see all of the Assortment Plan line items in one place. Below are the steps:
Go to Account > Data & Imports > Models
Select core data model titled Assortment Plan Item
This page will display all assortment lines that have been imported or generated in the UI.
Keep in mind that Assortment Plans are filtered collections of your Assortment Plan Items, on this page. When you create an Assortment Plan, it will pull in the lines that are relevant to the selected attributes and time frame.