Apologies if I’m the only one who didn’t know this, but this is one of those things where once you know, you’ll use it all the time.
I spent most of yesterday revamping my dashboard, the root card of each element is a custom card which doesn’t have a visual editor. By default the window in which you edit is often narrower than its contents so I spent hours frustratingly scrolling the contents of said window.
Today while making some changes I did something (at the time I didn’t know what) and a wide version suddenly appeared! I eventually realised that if you left click on the title of the editing window (Grid Card Configuration in screenshot below) it will toggle between normal and wide, Duh!!
As I said, apologies if this is common knowledge but I’m sure it will help someone. Regardless, I’m quite pleased with myself. 
Cheers 
Narrow
Wide
