Since version 3.0, not only plain text documents can be opened, but also folders. This feature allows you to organize your documents in a structured way, such as when you’re writing a book and want to keep separate files for each chapter. In order to open a folder, drag it to the application dock icon or select it from the Open panel, just as you would do for a regular file.
Since version 3.1, folders can be permanently linked as libraries to the sidebar. The sidebar can be opened either with a two-finger swipe to the right in any document window or from the View menu. Folders can be linked by dragging them to the popup button at the top of the sidebar or by opening them as described earlier and selecting “Link [folder]” from the same popup menu. If you later decide that you no longer want a specific folder linked to the sidebar, you can unlink it by selecting “Unlink [folder]”. Linked folders will appear with their plain name in the popup button, while open folders which are currently unlinked will appear with a “–” (dash) prepended to their name.
The sidebar displays all plain text documents contained in the selected library’s folder hierarchy. Documents can be opened by selecting them, while other actions are available from the context menu, such as opening a document in the Finder or printing it. Some actions are available for folders as well, so for example a print action executed on a folder will print all contained documents as a single file.