An experiment workflow typically consists of distinct parts like e.g. reaction, workup, purification, and others. Workflow separators help to structure your protocol by visually separating these parts.  

Note: 

When creating a new experiment, by default a "Reaction" workflow separator always is added to the top of the protocol.

So let's add a new workflow separator via the Protocol Toolbar:

The resulting protocol now looks like below:

The title of the new workflow separator is in edit mode now, therefore you can directly type a title of your choice, followed by the ENTER or ESC key. So let's type 'Purification' here: