If you right-click the background and select "Notes" under "View" you'll get a transparent box you can add comments too.  You can also do this to activities, that will tie the box to the activity with a dotted line

Hi Victoria ~ thanks for the reply.

for the note. is that only one note allow for every one view?

Thank you for marking my response as a solution!

Apologies - I'm a little unclear on  your question.  A workflow doesn't have multiple views, so yes there is only one comments box for the workflow as a whole.  But I think that's where the activity comments come in handy.  You can have your overall comments box for the whole workflow, and then more granular comments in the relevant activities/events.