The new GET_LIST() function allows to run a query against related records of any type: Linked Records, Sub-items, and Checklist Items.
For example: 
On the Customer level, I want to get the Total Amount of the three most recent Orders that are in Shipped status.
Let’s see how this can be done.
The Syntax
GET_LIST() can both filter and sort the related records.

Hence, it accepts four arguments:
A condition to filter by (Order’s Status)
A field to return (Total Amount)
A field to sort by (Order Date)
A sorting order, defaulting to “Desc” when not specified
Multiple conditions.
The function supports multiple filtering conditions that can be combined with AND or OR operators.
Also, the arguments for a field to sort by and sorting order are optional and can be omitted.
Working with the results.
The output of the function is a list of values.
The maximum number of values in a list can be controlled with the TOP() function.
Finally, a list needs to be wrapped with one of the aggregate functions:
SUM(), MIN(), MAX(), AVG()
ARRAYJOIN(), ARRAYUNIQUE()
CONCAT()
Use it with various field types.
This set of functions can be used in combination with any field type that returns an array, like Sub-Items and Checklists.
A formula below returns a name of a person assigned to an unresolved checklist item with the oldest Due Date.
