This is available for Graders.

If the question Author has enabled the Drawing Tool, you might see a Drawing forming part of the Candidate response. Drawings might be included on all question types. 

View Drawing

If Drawings are enabled on a question, a Drawing tab will be visible in Grading:

The Drawing interaction can also be seen in the Candidate answer with a quick link to that takes you to the Draw tab:

Zoom

Zoom option is available to allow zooming in/out on canvas. To see parts of the drawing outside the visible canvas when zoomed in, hold and drag to move the canvas around. Tip: expand the view to hide other options and focus on the drawing. 

Supplement to main answer

Note that Drawings can be enabled for any question type. It is a supplement to the actual question answer, and a question containing a drawing only will not be registered as answered, but the drawing will still be available. 

Drawings associated with automatically marked question types does not count into the automatic mark and should be reviewed manually. It can for example be used to show additional information or calculations leading to the final answer, and might lead to you override the automatic mark.