Full screen writing mode
Full screen mode to maximize writing space. Have a little "-" sign that minimizes the toolbar into a tiny chevron symbol. You can restore the toolbar by double tapping the chevron symbol.
Claudio Bottega commented
Please allow the app to go Fullscreen while editing a PDF document on Chromebook
I completely agree with this. The title bar does not need to be there all the time. Can you hide it just like in the view mode. This way we can use all of the screen. Also, displaying the same tool bar all day will cause burn in issues in the long run.