Using New Outlook on Windows for professional communication and productivity
What I have figured out is how to create a note for myself at the top of an email by going to "follow UP" > and where it says "Flag To" you can write a note there and it will appear at the top of the email so it is very helpful to you can type in 'next steps' etc. It is limited spacing though.
This is how it appears when you click on the email...