I'm beginning to like Gutenberg, but I find it too narrow, particularly when working with the 'Columns' block. Why is it so narrow, and can it safely be made wider? I could try doing so with CSS, but I thought it best to ask first, to avoid potential trouble.
The only way that comes to mind is to disable the options sidebar on the right. Just click on the cog icon and it will disappear, giving you 30px more space or so.
In addition, you can enter fullscreen mode by clicking on on the three vertical dots in the upper right corner all the way on the side and the choosing the respective option. This will disable the WordPress menu.
Not sure if that is enough for your purpose but it's what's available.