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function insertCheckbox() {
var sheet = SpreadsheetApp.getActiveSpreadsheet().getActiveSheet();
// Set the cell where the checkbox will be inserted
var cell = sheet.getRange('A1');
// Insert a checkbox in the cell
var checkbox = sheet.getRange(cell.getRow(), cell.getColumn()).insertCheckboxes();
// Set the checkbox value to true
checkbox.setValue(true);
}