doesn't appear to do anything. Cannot follow what the video is telling me to do.

Got it to work for Firefox Windows - eventually. Documentation on git not so good - watch the vimeo vid very carefully at start. It requires "Access your data for all websites". If you you go into the Addons > markdown viewer > manage > permissions: toggle "Access your data for all websites" it will NOT work. This setting will NOT stick. You will navigate, away come back, close firefox, whatevs and it will have reverted to OFF. HOWEVER, if you do as the video does at 00:30-00:40, you will receive the pop-up "Access your data for all websites" it will then work. NB. This is a brand-newey fresh install on windows. not a single other thing installed. It may well be a bug of firefox. I wasted a bit of time working this out. Given it's free, I prefer to give helpful feedback. Doc needs to be a bit more explicit - neither I nor AI picked it up. Thanks for the tool.

Settings are way to complicated.

Doesn't do anything. Firefox opens .md files as plain text, clicking on the extension icon only sets settings.

Кайф!

took a little bit of work to get file:// loads to render but was prompted to enable all sites and it's working now.

Does not work for me.

I installed in Firefox and followed the instructions to modify permissions but NEVER got it to work. Firefox would always display local files as plain text, never rendered. Perhaps a Firefox issue, perhaps some tricky configuration issue, but for me, wasted time trying to make it work. Removed the extension.

Great extension.
BTW, Is there a way that i can replace '..' with any other character as the parent path？

Does not register the .md file extension with the browser, so any attempt to open a markdown file leads to the Firefox "open with..." dialog. An alternative would be to add an "Open" button to this extension's panel, and have it properly open markdown files inside the browser pane. Otherwise this extension does not work at all because it is totally incapable of opening any markdown file.

Awesome, that's what I'm looking for :-)