Automatically Populate Custom Field for Saved Search

Hey everyone! I'm new to NetSuite and trying to help out a client who's been using it for years. We're trying to figure out the best way to accomplish the following:

This client has a saved search that pulls customer information so they can make their own call list. They want to add a custom field or sub-list to the saved search columns that includes recent activities so they don't have to open each customer record and view the activities. We also want make sure each customer only shows in the list once (so using the activity title and date fields as columns are out). Ideally, the saved search would look something like this: