If it returns query value to the database, put the checkbox

$(document).on('click', '.upd_glic', function(){
  var id = $(this).parents("tr").attr("id");
  $.ajax({  
      url:"editarglic.php",  
        method:"POST",
        cache: false,               
        data:{id:id},               
        dataType:"json",  
        success:function(data){

      for (var i = 0; i < data.length; i++) {
        Id = data[i][0];
        Validar = data[i][6];
        
        $('#idgli').val(Id);
        $('#validart1').prop('checked', Validar);
        
      }
        }
    });
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>

<a href="#" class="dropdown-item btn btn-warning upd_glic"><i class="metismenu-icon pe-7s-note"></i> Alterar</a>

<form method="POST" class="row g-3 insgli1">
  <input type="hidden" class="form-control" name="idgli" id="idgli">
  <div class="col-md-4 valt">
    <div class="form-group checkbox">
      <input type="checkbox" id="validart1" name="validart1" value="Sim">
      <label for="validart1"> Realizada correção com insulina após pesquisa</label>
    </div>
  </div>
</form>