As title indicates, I mainly use hackMD as a math notebook, and hence I use lots of LaTex to edit my context. However, I wanted to add some new commands as in overleaf but I failed. So I am curious that is it possible to define personal commands as in overleaf.

I have tried adding “newcommand{N}{mathbb{N}}” etc. in front of the whole text. Sadly, I still couldn’t replace mathbb{N} by N.
Can someone explain how it could be fixed and maybe some example is much appreciated.
Thanks in advance.