Zapier has posted a handy introduction to Markdown. There are a lot of these guides around, but they look to have done a good job here. If you are still mystified by how to use Markdown syntax, this might help. I am working on a bit of Markdown for academic work content, in the meantime, if this guide whets your appetite I also posted some links very early on to a YouTube series on using Markdown for academic writing
If you happened to have read any of the posts I have made about note-taking, you might think I have a problem. The real problem is not so much being torn between numerous different tools, but being torn between waiting on an old favourite to be reincarnated, so to speak, and moving on to something new. There are trade offs no matter which way you look at it. Apple Notes, for example, has some hard to overlook advantages – native integration means an unparalleled user experience when it comes to sharing material with the system-wide share extension on both the macOS and iOS. The Apple Notes share extension captures URLs in a form it calls rich links, which includes a thumbnail and text snippet to make captured links that much easier to recall. This rich text approach is both the major strength and weakness of Apple Notes, at least now that iCloud syncing has become so reliable and fast. Rich text relies on a proprietary database, meaning portability and future-proofing are open questions for notes kept in a system that relies on them. For that reason, I find myself only using Apple Notes as a kind of place holder for links I will use immediately, or when very basic collaboration is in order.
When it comes to capturing text as quickly as possible on the Mac, I have a hotkey set for nvALT, so it has become so ingrained that it just happens. You might wonder why I would recommend an app kept in the barest of maintenance cycles while the developer openly builds its replacement. To which I would suggest that first, I can’t imagine Bitwriter will depart from the nvALT workflow much at all  – the user base for Bitwriter are nvALT users, so moving to the new app will be trivial when it happens. Second, even if there were significant changes, this is the beauty of plain text, moving to another app will not break your system. Having said all that, I have recently been made aware of another Notational Velocity  clone out there that is in active development. So if you are looking for an a lightweight plain text, open source, note-taking app, then FSNotes is worth a peek.