You can add a block of empty or clear space between paragraphs of text by clicking on insert spacer from the insert bar that appears at the start and end of each text paragraph.
An area of "empty" space will be added. The space is shown with a green highlight and the word 'SPACER' when you mouse over it in the editor, so that you can see its size. The green highlight and label aren't shown when you mouse away from the area, and aren't shown at all in the story preview or when the story is published.
When hovering over the space in the editor, you are also provided options for increasing or decreasing the size of the spacer and to delete it.
Alternatively, the space above and below a block can be set uniformly in a single action by using the text formatting menu within a block, as shown below:
When using this Block spacing option in the Text formatting menu, the area it affects is shown briefly highlighted in light orange. The slider allows for easily increasing or reducing the space before and after a block, while the settings menu to the right of the slider enables more fine-tuning of the space by setting a numerical value.