Cross-selecting email from sidebar in normal view

The agenda is a great feature and comes closer to how I work with emails (emails lead to tasks etc.).
Having an email in the agenda I’m not able to select just this email in the normal view. Double-clicking it opens a new window. For me this is not optimal since this email is not a part of the whole client anymore. It would be way better if the email gets just selected in the normal view, cause that’s where I do stuff with mails, not in a seperate window. I don’t like having opened a couple of seperate windows (more clicks etc.).

I guess a cross selection feature would require a minimum of implementation time. What do you think?