Pete, I know you didn't ask for advice about Joplin, so apologies for this unsolicited advice: configure the built-in backup plugin to auto-backup your notes every N hours/days, somewhere on your system drive. Better to have more than a single backup (the default value, I think, is seven).

After setting it up, test your configuration for accuracy of backup and for ability to import it back into Joplin.

Why do all this?
Given the vagaries of various operating systems on smartphones and desktop computers, and of the connectivity between devices, synchronization is a tricky business for any cross-device, cross-platform app. There may be race conditions, or the connection may abruptly fail, or the operating system may throttle or kill the synchronization for whatever reasons; so data loss can happen. If you have a backup copy, you can simply import the lost data, and get back to work.

Also, your backup plugin may create a backup after data loss happens, but before you register the loss. In such cases, having multiple backup copies allows you to use the best version to recover your data.

Remember also that Joplin itself retains note history (by default, for 90 days), so recovery of lost data should be possible within the app itself. But I do think setting up multi-copy auto-backup outside of the app's operating zone is still good practice.

Ignore if you have already done this. 😄

Like you, I use markdown to write notes in Joplin. And to write Fedi posts such as this one. (wafrn, the Fedi software I am using, supports writing posts in markdown.)

My only suggestion: do not get seduced by markdown's ease of use. Do not try to use it indiscriminately. Do not use it for documents that require complex markup (text with lots of subscripts/superscripts, mathematical equations, chemical formulae, nested sections, tables, columns, etc.), or even for simple but very long documents (long-form writing, books).

Basically, limit its use to short documents/notes that require very little markup.

This article is a good overview of the benefits and limitations of markdown.

As an aside, I hope djot replaces markdown as the most popular lightweight markup language in the near future.