Is there any Linux software where I could edit rendered Markdown (preview)?
I know that I could edit the text file directly. But I was wondering if some software let me edit the rendered HTML and text file could get updated?
It sounds like what you really want is a "WYSAWYG" (What You See Approximates What You Get) editor for MarkDown. If that's actually the case, I can point you to Typora; I use the Windows version, and it works nicely.
I don't recommend Typora, as it is closed source. I found: