Both Price List and Price Grid store the header (dashboard-like price list header) inputs, outputs and chart in the configuration field of the Price List/Grid entity.
Mostly you will need to use headerInputs which contains the values entered by users to the header inputs.
Values
inputs – Input fields defined in a Price List / Price Grid logic and entered by users on the Parameters page when defining the Price List/Grid.
headerInputs – Input fields defined in a Price List / Price Grid header logic and entered and saved by users on the header dashboard-like part of the page.
outputChartDefinition – Definition of the chart, displayed in the middle part of the dashboard-like Price List/Grid header.
outputs – Result values of the Price List dashboard-like header.
This configuration information is stored as a Map, but in a JSON format.
Example: What is available from api.currentItem() in a Price List header logic
Map currentItem = [ label : "PricelistHeader", configuration : ''' { "inputs": [], "headerInputs": [ { "name": "SpecialAdjPct", "label": "Enter Special Adjustment (in %)", "type": "USERENTRY", "value": 0.02 } ], "outputs": [], "outputChartDefinition": {} } ''', priceGridType : "SIMPLE", headerTypeUniqueName: "PricelistHeaderType", id : 363 ]