It is a huge benefit to be able to open text area contents in a real text editor for serious text editing jobs.
For Chrome, there is the GhostText extension, and it seems to be actively developed. It has plugins to support, for instance, Atom, Vim, and Sublime text.
The It’s All Text! extension for Firefox adds a context menu item and small button to text areas on web pages. By activating the It’s All Text action, the text area contents are opened in the user’s preferred text editor application on the PC.
Whenever the file in the text editor is saved, the web page is synchronized and updated within a few seconds.
This is a dream come true for editing Markdown text and other markup formats, program source code, and taking advantage of advanced search-and-replace features in a full-featured text editor like Vim (GVim), Notepad++, etc.
Unfortunately, It’s All Text! is not compatible with the new Firefox 57 extension framework so it is being discontinued.