Have Windows Explorer preview markdown files

I don't have enough reputation to add a comment, but, the solution to your problem is the correct answer from this thread: Windows 7 - Preview other file types as text in Preview Pane

Edit: Actually, according to this guy in that same thread, using PreviewConfig should be enough.

Edit 2: In order to preview custom or non-standard file-types with actual rendering (eg. color for code, rendering markdown, or images), it seems you need to have a Preview Handler. This thread on another forum adds some useful information to the discussion of developing such a preview handler, particularly this tutorial written in C#. I tried searching for a pre-written .md preview handler, but have come back empty handed. If you know C# I highly suggest looking further into this.

Bit of an old thread, but this (a bit unstable) extension (warning: I am the author) does the trick for me:

https://github.com/Atrejoe/MarkdownPreview

Installation is a bit of a drag though.

since a couple of days this is possible with the MS PowerToys.

Microsoft PowerToys is a set of utilities for power users to tune and streamline their Windows experience for greater productivity. Inspired by the Windows 95 era PowerToys project, this reboot provides power users with ways to squeeze more efficiency out of the Windows 10 shell and customize it for individual workflows. A great overview of the Windows 95 PowerToys can be found here.

After you have installed it, you just toggle on the option "File Explorer" on and you get the rendering you want. Links are not clickable yet, but apart from that it looks nice.

It comes under an MIT license and can do other useful stuff.