Mellel is not available for Windows but there are plenty of alternatives that runs on Windows with similar functionality. The best Windows alternative is LibreOffice - Writer, which is both free and Open Source. If that doesn't suit you, our users have ranked more than 50 alternatives to Mellel and many of them are available for Windows so hopefully you can find a suitable replacement. Other interesting Windows alternatives to Mellel are Notion (Freemium), Microsoft Word (Paid), Manuskript (Free, Open Source) and Scrivener (Paid).
With so many tools, it's hard to keep everyone on the same page. Notion is a new tool that unifies them all. It's like Google Docs, but everything is organized and discoverable by your team. Real collaboration in real-time.
Manuskript is an open-source tool for writers, with outliner, character management, plot development, distraction-free editor, etc. Outliner Organize your thoughts and snippets in a hierarchical manner. Organize them as you wish, reorganize them on the go.