The reset button

The reset button appears to the left of the name of the tool you're using and looks like two arrows pointing in opposite directions:

The reset button returns you to the starting point of the tool you're using, as if you had entered the tool in a new session.

Note: If you return to the starting point of the tool before saving (e.g., before choosing to add, post, save as draft, etc.), you will lose any information you have entered.