To split cells, select the merged cell and do one of the following:
–On the Home tab, in the Table group, click
Unmerge cells.
–Right-click the range and select Unmerge cells from the context menu.
–When working in macOS, run the Format > Table > Unmerge cells command from the command menu.
–Press Alt+Shift+M (Windows, Linux) or ⌥Option+⇧Shift+M (macOS).
The data that is contained in the merged cell is placed in the upper-left cell of the resulting range. Cells in the range will retain the formatting of the merged cell.