Sending a report to a list - how to set and pass variables?

Hi,

I'm trying to build a workflow that sends one of my custom made report to a list. I'm fallowing these process: https://docs.campaign.adobe.com/doc/AC/en/WKF_Use_cases_Sending_a_report_to_a_list.html

My issue is related to variables. First step of my report's template is choosing dates (time range of report).

Dates are stored in two variables: endDate and startDate:

My question is: how to set and pass these variables to xtk.report.export method (launched in JS activity)?

My code:

var reportName = "throughputNew";

var path = "/home/reports/"+"throughputNew"+".xlsx";

var exportFormat = "OOXML_SS";

isAdHoc = false;

var _ctx = <ctx _context="global" _reportContext={reportName}/>;     ///// I guess variables should be set up somewhere here, but how?

xtk.report.export(reportName,_ctx,exportFormat,path,isAdHoc);

Thank you in advance,

Marcin