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.