Today I learned it's possible to center code in JetBrains products. This is apparently part of what they use to support the distraction-free mode. If you don't want to completely get rid of tool Windows, etc. but still want to center the code, you can use this Stack Overflow post.
Essentially, it comes down to going to Help -> Edit Custom VM Options then enter -Deditor.distraction.free.mode=true.
Craft on.