The correct mapping is Dynamic Widget Field with a Selection interaction because the flow input must depend specifically on a value that the user selects in another dashboard widget. Salesforce distinguishes two dynamic interaction types when mapping dashboard data to Salesforce Flow inputs: Selection and Result. A Selection interaction passes the value resulting from the user's selection in a widget, whereas a Result interaction passes a value derived from the widget query results.
A Static String would supply the same manually configured value every time and therefore cannot satisfy a requirement in which the flow input changes according to what the user clicks.
Operationally, the consultant configures the Salesforce Flow action, identifies the required flow input, selects Dynamic Widget Field, chooses the source widget and field, and sets the interaction type to Selection. This creates an actionable analytical experience where a user's interaction with dashboard data can directly feed contextual values into a Salesforce business process.
References/Topics: Visualizations and Dashboards - > Analyze and Share Data - > Add Single-Click Actions to Your Data - > Salesforce Flow Actions.