Joining and splitting cells

You can join adjacent cells of the table. As a result, there will be one big cell. In order to do this:

select the first cell with the help of a mouse;
left click and, without leaving it, move the mouse in order to select the group of cells;
on the selected region, right click the mouse in order to show the context menu of the cells;
in the context menu, choose the "Join cells" item.

In order to split a cell, call its context menu and choose the "Split cell" item.