https://docs.servicenow.com/bundle/vancouver-build-workflows/page/administer/flow-designer/concept/inline-scripts.html

// For Create and Update Record
var shortDesc = fd_data.trigger.current.short_description; // Get Short Description
var flow_variable = fd_data.flow_var.fvar1; // Get and access flow variable
var change_number = fd_data._1__update_record.record.number // To access Change Number from previous steps.
var assignment_group = fd_data._2__for_each.item.assignment_group; // To access in for each loop.
var change_fields = fd_data.trigger.changed_fields; // Return field change value

// For Service Catalogs
var variable1 = fd_data.trigger.request_item.variables.test_variable; // To access variable value
var request_desc = fd_data.trigger.request_item.description; // To access request description

// For Inbound Email Application
var email_sub = fd_data.trigger.subject; // to get inbound email subject
var email_body = fd_data.trigger.body_text; // Get Email Body
var email_inbound = fd_data.trigger.from_address; // Get Inbound Email address