A prose writer here, not a coder. Or, rather, only a very rudimentary coder.
A couple years ago, OdatNurd graciously helped me–here–with the creation of a brief syntax definition that (along with some changes to my color scheme and key bindings) allowed me to quickly insert highlighted comment lines inside my txt files.
I was a txt-only enthusiast for a long time, but now I’m switching over to Markdown and I’m hitting some confusion.
Thanks, I think, maybe, to that creation in 2020 of the new little syntax definition, I had a syntax called “my plain text file type” or something like that.
I’ve now been fiddling with the syntax/color/and binding files we created back in 2020 because I wanted to have that highlighting ability we created then, but operable in .md files.
So I now have something called “My md file type”, a syntax that lets me use those highlighting tools we created, but in md files. And it works for that purpose.
BUT, when I use that syntax, I no longer have the other parts of the full Markdown syntax available, and I want them. At this point I can choose either Markdown syntax or “My md file type.” I can’t have both.
I’m an ignoramus about many thing, including syntax definitions, but what I’d like to do is somehow combine the highlighting capabilities of “My md file type” with the full capabilities of Markdown, i.e., to combine them into a new syntax definition, I suppose. I’ve looked all over and can’t get my head around how to do that. And Chat GPT was not much help. 
Any hints, pointers, advice would be much appreciated. Sorry for the long post.