It doesn’t quite fit your requirements, but org mode from emacs is very close.
.org files instead of .md, and the preview does require a bit of config, but it’s not as bad as some make it be, especially if you pickup a preconfigured emacs “distro” (like doom emacs for example) in which case I think it’s just a feature flag to set to on.
Org is also very appreciated for it’s TODO features, which you seem to make a big use of.
It probably isn’t a match for you due to the markdown requirement, but I’m mentioning it just in case you didn’t consider it in the past.
It doesn’t quite fit your requirements, but org mode from emacs is very close.
.org files instead of .md, and the preview does require a bit of config, but it’s not as bad as some make it be, especially if you pickup a preconfigured emacs “distro” (like doom emacs for example) in which case I think it’s just a feature flag to set to on.
Org is also very appreciated for it’s TODO features, which you seem to make a big use of.
It probably isn’t a match for you due to the markdown requirement, but I’m mentioning it just in case you didn’t consider it in the past.