My suggestion is to do what I do: prepare the post in a text editor on the PC, and when it's ready, minus only the images, transfer it to the browser.

I use BBEdit on the Mac, which displays markdown and so lets me see what the result will be. There may be text editors under Windows and Linux with the ability to display markdown as well.

Just as a point of interest, losing a post is always a risk when dealing with any web site. You can lose it because the site goes down, the Internet between you and the site goes down, transmission errors / loss, problems with the site's posting capabilities, and so forth.

So it's a nice, safe conservative approach to create your post in a text editor, then copy/paste. That way you can't lose your work, plus you have a local copy you can save if you like.

This may be possible on a phone as well, depending on available software, clipboard, and so on.