The session record button IS NOT the record button next to the stop and the play button. The session record button is near the top center of the screen, next to the “new” button. This button is only available in Session View. When pressed, the session record button will record a new clip in all armed tracks (midi and audio) if an empty scene/row is selected. For midi clips, if you press the session record button and are playing an existing clip, you will OVERDUB new notes to add to existing ones.