cmd+shift+v in VSCode gives a nice preview of the current markdown file. I recommend trying it out if you haven't already :)
ETA: This is actually how I draft all my SN posts - markdown in VSCode, then preview in VSCode too.
I use it a lot for the newsletter but it's not as pretty.
This is further complicated by me preferring to code in light/grey mode but preferring to read in dark mode lol.
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