If currently no cell is selected, a new row will be inserted at the bottom of the table. If currently cells are selected, as many new rows as the selection has will be inserted below the selection.
如果当前未选定任何单元格，则会在表格末尾处加入一个新行。如果当前有单元格被选定，则会在选定区域之下插入与选定行相同数量的新行。