Is there a markdown editor which let me open .md files from Windows?

I can't recall if Sublime does, but VS Code offers a preview pane which you can place side-by-side with your markdown. I sometimes use it when editing complex documents.

However, I think OP is asking to have the formatting be in-place, for true WYSIWYG editing. This usually works okay for things like bold or italics, but is trickier to do elegantly with list items, quotations, and things like that. Not impossible, but I generally only see this used where Markdown is limited to a stricter subset of features, such as in Discord's editing field. I don't know of any tools off the top of my head that offer full markdown features in-place.

As for the requirement of being able to open files using a native Windows file picker, it might be easier to get into alternate workflows such as dragging files to the editor window, or using default file associations. Unfortunately a lot of tools do use their own file browsers or tree structures, especially those that are based around a "project" workflow (like Godot).

This - npp has a very extensive suite of plugins that will format almost any ASCII file content in the chosen standard - markdown, XML, HTML, etc. The PrettyPrint plugin makes blobs human-readable as well.

While obsidian does use md files, it’s not really convenient as an editor for an md file you have lying around. To my knowledge, you can’t just open an md file with obsidian, you’d have to move it into a directory where there’s an obsidian vault and then open that vault. Perfectly fine if that’s where you want that file anyway, but annoying otherwise.

Do you sync Joplin? I find the dropbox sync to be very buggy on Android. I often have to go and manually clear the lock files in dropbox. And even then I sometimes lose content of things that are too far out of sync. I'm wondering if the paid for or self hosted Joplin server is more reliable, if you have any experience with either.

Typora is very good except it costs money (used to be free, now it’s a 15-day trial).

Oh, that's why I haven't been able to update it when it asked me to - I hadn't yet checked the website. I'll keep hold of my outdated free version then!

A Glorified Bucket is better than a Regular Bucket, you can actually search stuff from the glorified one =)

Obsidian is nice with a few tweaks to ditch the padding

.cm-s-obsidian {
	padding-right: 0px !important;
	padding-left: 0px !important
}

.view-content>.markdown-source-view.mod-cm6>.cm-editor>.cm-scroller {
	padding: 5px 10px 0px 10px !important;
}

I like that it gives a live preview instead of leaving the markdown in place.