In case anyone isn't aware, the trick is to create a group with any contact and then remove them. Mine is pinned to the top and named Notes - and unfortunately is the most robust way to share images and notes from desktop to Android (I tried Pusbullet and Join too)
Another option that’s cleaner imo is to literally start a chat with yourself as OP mentioned. Simply navigate to this URL on your phone https://api.whatsapp.com/send?phone=$1
Replace $1 with your phone number including country code but without a + sign.
People sending themselves emails or whatsapp messages was certainly one motivation for the interface. I personally also wanted a) reminders associated with notes, and b) simple lists so I don't have to use separate apps for different types of notes.