The cascading list type synchronizes simple string lists with sub lists.
In the following we will use a data source with this JSON result:

{
   "parentList": [
    {      
        "name": "Mario Speedwagon",
        "children": [
            { "name": "Andrew" },
            { "name": "Mathew" }
        ]
    },
    {      
        "name": "Anna Sthesia",
        "children": [
            { "name": "Margret" },
            { "name": "Anthony" }
        ]
    }
  ]
}
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Select Parent List

First select the parent list

$.parentList[*]
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Parent Label

Relative to the selected list define a path to the parent label

$.name
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Select Children

Relative to the selected list define a path to the children list

$.children[*]
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Child Label

Relative to the selected children list define a path to the value representing the label

$.name
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Limitations

The Cascading List type allows up to 1.000 parent values.