Try Tools > Customize > Options > "Always show full menus".
Playing around I can see that you can add to or edit the body text as
well. Right Click on the email body and select EDIT MESSAGE. Again
Ctrl+S will save your changes. Great to add notes to an email!
Call Becky to discuss
Check facts with Steve
Once entered, the reminders are visible in a grey band at the top of
the email, whether viewed in the Reading Pane or opened fully. You can
also add timed alerts to the reminders.
To do it, right-click on the flag next to each email and select "Add