You can use this website, log in using the extension. It has a proper Markdown format editor. Whatever you post there will also show on Damus as a post/article. However, it will not open any external website; instead, it will render in Damus as a note but with proper headings and subheadings.

It's very new space, it's all coming together. It needs some time.

Website: https://habla.news/