code: function hGrow(xx, edge) {
        const cells = [];
        for (y = range.top; y <= range.bottom; y++) {
          const c = matrix.findCellAt(sheetName, y, xx);
          if (c && c.mark) {
            cells.push(c);
          } else {
            return false;
          }
        }
        range[edge] = xx;
        for (let i = 0; i < cells.length; i++) {
          cells[i].mark = false;
        }
        return true;
      }
docs: grow horizontal - ensure all rows can grow