onEdit() 'row is not defined' error using checkboxes

This script tries to add or remove checkboxes from column A if columns B-D are populated or not. If every cell in those three columns of that row is populated then a checkbox is inserted in column A. If even one cell in those three columns of that row is not populated, then no checkbox is inserted.

column A = checkboxes

column B = title

column C = tstart

column D = tstop

function refreshCheckboxes(){  let sheet = SpreadsheetApp.getActiveSpreadsheet().getSheetByName('sheet_name');  var rows = sheet.getDataRange().getValues();  var headers = rows.shift();  var checkbox = row[0]  var title = row[1];  var tstart = row[2];  var tstop = row[3];  for (var i = 0; i < rows.length; i++) {      if (rows[[title][tstart][tstop]] !== "") {        checkbox.insertCheckboxes();    } else {      checkbox.clearDataValidations();      checkbox.clearContent();    }  }}

CURRENT OUTCOME:

ReferenceError: row is not defined is occurring when the row variables are being set. I'm not sure why I'm getting that error because I have similar functions that define the row variables in this way. My other worry with this script is about how columns B-D are set up. Is an array appropriate here and and is there an better way to set this up?

DESIRED OUTCOME:

To identify what is causing the row definition error and correct it. To verify if that AND() functionality works.

I already have an onEdit() that works perfectly other than it applying to only one row at a time thus I wanted to make a custom to run as needed.

Thanks!