This option lets you to add any kind of statement into the function such as “Return” or ”Exit” commands. Although you can use this to make conditional statements or equations but it is not recommended.

After inserting a text into definition, it will appear as a simple button labeled by the Expression text.
To edit a text in function simply click on it.
To remove the text, right click and choose delete option. Also you can duplicate or copy or cut a text via this menu.