> A simple derived exporter?  Or (on the LaTeX side) the comment package?
> 

Thank you. I managed to achieve this with the following code:
(defun my/latex-remove-NOTES-blocks (text backend info)  "Filter special blocks from latex export."  (when (eq backend 'latex)     (if (string/starts-with text "\\begin{NOTES}") "")))
(eval-after-load 'ox '(add-to-list                       'org-export-filter-special-block-functions                       'my/latex-remove-NOTES-blocks))

This was the first emacs-lisp code that I wrote with knowing what I was doing. :)
Best,Joon