You cannot delete a cell on a Grid type of page. You can delete the row or column that the cell belongs to. You can delete a cell on a Freestyle type of page.
Choose Edit > Edit mode (F2).
Select the cell you want to delete.
CAUTION:
This is only possible with Freestyle page types!
Do one of the following:
Press Delete.
Right-click the selection and choose Delete from the shortcut menu (only for Freestyle page types).