A few months ago I got a new computer that has hardware with little Linux support, and so while waiting for someone to make a sound driver, I’ve been using Windows 10. I tried a lot of text editors, even building Gedit from source, before settling on Notepad++.
Notepad++ has built-in syntax highlighting for a lot of languages, but not Markdown. You can make your own “user-defined language”, and several people have created ones for Markdown, but I wasn’t really satisfied with any of them. So I made my own, which you can check out on Github. Due to the limitations of user-defined languages, some Markdown features can’t be implemented (e. g., asterisks as bullets, three spaces to create code blocks, etc.), but it should be good enough for everyday use. Please try it out, and adapt it for your own use!