@roy_vaixel Text Blaze cannot perform system commands such as Ctrl-c, Ctrl-v. However, since you are in Lightning and emailing exclusively through the case, you can use the Salesforce merge field code to insert the case description contents directly into your email. The code is {{{case.description}}}. You simply type that into the body of your email and when you send it, the code will be replaced with the case description contents for the recipient to read. That’s likely the most smooth way to do it. There is a way with Text Blaze using some RegEx coding, but, because you can, may not mean that it’s the most ideal solution.
I hope this helps! Forgive me if you are already familiar with SF merge fields. Otherwise, if you’d like to chat more about them and even explore some cool ways to use TB with SF, let me know!