I remember there was a time that when you type # in R markdown it will immediately transfer to the heading output. Also, when you type **bold** it will immediately show the text in bold. But now I can't find a way to do this.
Is it possible to show the markdown output in the .rmd document? Thanks!
This behaviour will depend on the text editor you use. Some Markdown editors have a "What You See Is What You Get" (or WYSIWYG) philosophy that will do exactly what you describe. You can find examples of WYSIWYG Markdown editors online, I personally have only tried Typora. But as far as I can tell, none of them seem to support Rmarkdown (perhaps someone has made an Rstudio add-in?).
On the other hand, in the early days of knitr, it used to support Lyx (I don't know if it still does), which is maybe closer to what you have in mind? See this post for an example: https://yihui.org/knitr/demo/lyx/
