How to insert a newline in the middle of a client message

In the text box I can add a newline only before and after of a client message by clicking on the read square with the arrow. We use 4.4.3 version. How to insert a newline in the middle of a client message?

And how to insert a newline without a mouse or a touchpad?

Is this when quoting something? I believe the CKEditor allows for shift+enter to also create a new line while in a quote block.

I have attached a screenshot, where I can create a newline, and where I can not create a newline.

Perhaps the format is fixed. Change the formatting.