That is what I want (with out plugins and with out including shortcodes to all posts)
Headings h1-h6. Gather decrease headings and textual content.
Instance:
Like Microsoft Phrase. (Like this file)
Hyperlinks that had been much like my request however didn’t assist (or I couldn’t):
https://stackoverflow.com/questions/37358608/how-to-add-automatically-collapse-expand-in-content-wordpress-single-php
https://jupyter-contrib-nbextensions.readthedocs.io/en/newest/nbextensions/collapsible_headings/readme.html
https://wparena.com/how-to-expandcollapse-wordpress-posts/
https://stackoverflow.com/questions/61802692/add-shortcode-to-all-post-types
Any assistance is appreciated.