This article explains how to manage the Lookup and Multi Lookup fields.
There are two field types available for creating new fields: Lookup & Multi Lookup. Lookup fields are valuable for creating relationships between plans in the system. If the plan types are set up in a flat hierarchy, use lookup and multi lookup fields to create the parent to child relationships. If the plan types are set up in a hierarchy, lookup fields automatically get created and populated with the parent value for the children plans. Views can be grouped and filtered by the lookup fields. Ex: A plan can have a lookup to the program-type plan(s) to which it's associated. Or, a feature-type plan can have a lookup to the epic-type plan(s) to which it's associated.
Follow the steps to create a new plan-level field. For more information, refer to Create and edit fields.
Field Type: Select Lookup or Multi Lookup.
Lookup Plan Type: Select from which plan type the users will select the lookup field.