macOS Sierra (which I almost forgot comes out tomorrow!) includes a new feature for developers to use tabs in any windowed app. You probably already use tabs in your web browser and Finder gained tabs in a recent OS X update, and macOS Sierra makes using tabs in other built-in apps like Text Editor possible.
Byword is a well-known text editor for the Mac that I personally use to draft stories and edit text for work when I’m not writing in WordPress in Safari. The latest update now lets you collect multiple Byword windows into a single Byword window with tabs just like Safari or Finder.
It may be a limitation of macOS Sierra, but keyboard shortcuts don’t seem to create new tabs, just new windows. You can use the UI to add new tabs once you collect multiple windows into a tabbed window, however.
What’s New in Version 2.7
Improved support for macOS Sierra.
– Tabs: Merge multiple documents in one window; Use menu Window > Merge All Windows; – Improved performance in Markdown rendering; – Bug fixes.
Byword for Mac is available for $11.99 on the Mac App Store.