Keep a note off the client page
Mark a comment internal and it stays on your side, at the same timecode as everything else.
Above the comment box there is a small control that says Public. Press it and it says Internal, with a padlock instead of a globe. Anything you write while it says that is yours alone: the client page never loads it, and it is not counted in anything they see.
It is the same thread and the same waveform, so an internal note sits at the timecode it belongs to rather than in a separate document you have to keep open. Reminders of what you changed, the thing you want to try if they ask for another pass, the reason you left the low end where it is.
The control remembers nothing between comments. Every new comment starts public, because a note that was meant for the client and quietly went private is the failure that matters here.
Not covered here? Write to support@soneam.com.