Is it possible to show also the email contacts in chat sidebar?

So I could see all my contacts together and send email by just a click

It is not possible at the moment but we will consider it and maybe will implement it in the future.

Actually it already was implemented in version 4 as I can see here…

The other obvious option would be changing the action of double clicking on a contact in contacts section to send email instead of edit contact.

But I think contacts on the sidebar would be nicer.

Yes it was, but we decided to remove it as part of the design changes.