A sidebar for signatures and text templates in Mail Composer

In the ‘New Message’ window, you can add a sidebar for signatures and text templates. (like your great sidebar in the main window)
* Clicking a text template would insert the text at cursor position.
* Mouse over the template lines would show a small preview of text template.
* Templates would be listed only for selected mailboxes.(only selected templates
will be visible for a certain mailbox composing)
* Add, Edit buttons at the top of this sidebar.
* Template groups for a further improvement.

I mentioned this, as I use a lot of small text templates. And it is a time consuming
selection. For every template, I go to signatures list, then I go
down ‘Insert on caret position’ then select it from the second long list. I tried to sort them by putting grouping letter at the definitions start but it does not help much.