tl;dr:
Use this pattern in Omnistudio Integration Procedure to efficiently collect JSON nodes from a JSON list.
This is an alternative to looping through a JSON list using a Loop Block and collecting nodes.
Loop Block in an Integration Procedure needs careful consideration and often results in value sets that needs to be corrected. This approach avoids such issues.

Use Case

JSON list that needs to be separated based on a node value in the JSON.

Prerequisites

This approach uses Omni Studio low code tooling.
It assumes that the JSON list is within an Integration Procedure.

Approach

Retrieve the list of JSON to a node - likely from a Data Mapper. Use the List Action, list the Merge List Order to the JSON list. Use the Filter List Formula to indicate condition where the item in the JSON should be acted on. The output would now be available for that List Action.

Add additional List Actions with Filter List Formula to achieve other lists.

Assume Input JSON List

[
    {
        "Name": "Customer 1",
        "Type": "Residential"
    },
    {
        "Name": "Customer 2",
        "Type": "Commercial"
    },
    {
        "Name": "Customer 3",
        "Type": "Residential"
    },
    {
        "Name": "Customer 4",
        "Type": "Commercial"
    }
]

After two List Actions, with Filter List Formula that checks for type value.

{
    "Residential": [
    {
        "Name": "Customer 1",
        "Type": "Residential"
    },
    {
        "Name": "Customer 3",
        "Type": "Residential"
    }
    ],
    "Commercial": [
    {
        "Name": "Customer 2",
        "Type": "Commercial"
    },
    {
        "Name": "Customer 4",
        "Type": "Commercial"
    }
    ]
}