Edit

[gionuci]

Hello, can I edit already scheduled mail?

[jph-sendlater]

You can open the message just like any other, but when you do that the schedule will be removed (as a precaution to prevent you accidentally sending a message that you are currently modifying). You will have to re-schedule it when you're done editing.

PS: I just saw your email, but thanks for moving this to github! I'll respond here instead.