How to add an extra Module tab

How to add an extra Module tab

Hello, 

I wonder if you could help figure out how to add an extra Module tab to the agent ticket.
Free editable text/comment type of field ideally 
I know the option is not readily available, only option here is to separate comment from Conversation by selecting Thread but I need an extra

See below screenshot




Some help would be awesome as I think this would be a very beneficial topic for many.

Many thanks, 
Hasna