Second that. Markdown is about lightweight, requiring just a text editor and a few neurons to memorize the markup.

Markdown already handles 'attachments' via tag for image or HTML anchor for other file types. Prettify via CSS.

Global search and replace indeed needs an extra effort. If faced with such a need, I'd just use any of active IDEs already installed, well, Atom should do.

Adding "attachments" like that, the way Boostnote also does it, is not portable nor ergonomic, since you need the full path to the file in question or you need to upload it somewhere.

What? Just use a relative path.

It doesn't tick all the boxes though, there's no good way of adding attachments to notes and the moment a note should be categorized into 2 or more folders the all thing falls apart.

Granted on the folder side of things, but adding an attachment is really just dropping it into the folder on the filesystem side.

You can't just paste it like you could with other apps on Windows though, and youll need to do a tiny bit of manual work - granted!