How do I add or remove a single cell in a table?

| 1 | 1 |

| 2 | 3 |

| 3 | 4 |

| 4 | |

Now I want to add an empty cell in @2$2 (below the heading) and thus move the following cells in column 2 down one step.

After:

| 1 | 1 |

| 2 | |

| 3 | 3 |

| 4 | 4 |