Switching to layout editing mode

To edit layouts, go to the Layouts tab. To switch to editing mode, click the  button to open the context menu of the layouts ribbon. Select Edit layout.

In layout editing mode, space is divided by a grid of equal-sized squares for holding viewing tiles (1).

On the edge of the layout there are grid square fragments (2), which are parts of ordinary empty cells and allow adding new cells to the layout (see Adding new cells to a layout).