In November 2016, we announced the release of a new document editor and kept the older "classic" editor available temporarily while we continued to improve the new editor. Every element of the document editor was rebuilt to deliver a more modern editor and improve your experience when creating documents. For example, in the new version we introduced auto-saving, the ability to copy and paste or upload images and have them display inline, and also the ability to resize inline images.
As of this week, it's no longer possible to activate the classic editor feature in your documents. The older editor and editing toolbar have now been completely phased out. This means you'll have the new toolbar and a rebuilt input field when editing Quick Notes and text-format-enabled text fields in flexible assets, which provides you with a more consistent editing experience.
As always, we'll continue to improve the new document editor. If you would like to see specific features and improvements, continue submitting or upvoting ideas in our feature request portal.