Yes! You could use the "Private Notes" section to add comments about the call that you just took.
A short video:
1. Click on Inbox
2. Click on any of the calls
3. You can add your notes in the Privates notes section and click on notes.
And when you enter comments & "Add Note", It looks like this:
Please note that the notes entered in the Private notes section can only be viewed but cannot be downloaded for now.