Automatic dialog helps finding the correct template right there where you type.
Imagine that you have a template that explains to your users that they have to check their spam inbox:
Title: Add note about Spam folder Body: Note: If you can't find the e-mail, please check your 'Spam' folder in order to find the missing e-mail.
Now when you hit CTRL + Space in the body of your e-mail a small popup will appear where you can choose the correct template.
You can find the above template by typing spam for example. It will match it because it finds it in the title.
The CTRL + Space keyboard shortcut can be changed in Settings.