Enhances headers (or any elements) with link icons on hover - https://lukasznojek.com/blog/2019/08/automatically-enhance-headers-with-hierarchy-and-links/

addLinkIconsToHeadings.js

/**
 * Enhances headers (or any elements) with link icons on hover
 * 
 * @param {string} sectionSelector - id or class of the section that contains the headings, e.g. '#main'
 * @param {string[]} elements - array of tags that should be changed, e.g.: ['h2', 'h3', 'h4']
 * @param jQuery - reference to the jQuery
 *
 * Style the result in .header-link
 */
function addLinkIconsToHeadings(sectionSelector, elements, jQuery = $) {
	// icon (C) https://fontawesome.com/icons/link?style=solid
	const svg = '<svg aria-hidden="true" focusable="false" data-prefix="fas" data-icon="link" class="svg-inline--fa fa-link fa-w-16" role="img" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512"><path fill="currentColor" d="M326.612 185.391c59.747 59.809 58.927 155.698.36 214.59-.11.12-.24.25-.36.37l-67.2 67.2c-59.27 59.27-155.699 59.262-214.96 0-59.27-59.26-59.27-155.7 0-214.96l37.106-37.106c9.84-9.84 26.786-3.3 27.294 10.606.648 17.722 3.826 35.527 9.69 52.721 1.986 5.822.567 12.262-3.783 16.612l-13.087 13.087c-28.026 28.026-28.905 73.66-1.155 101.96 28.024 28.579 74.086 28.749 102.325.51l67.2-67.19c28.191-28.191 28.073-73.757 0-101.83-3.701-3.694-7.429-6.564-10.341-8.569a16.037 16.037 0 0 1-6.947-12.606c-.396-10.567 3.348-21.456 11.698-29.806l21.054-21.055c5.521-5.521 14.182-6.199 20.584-1.731a152.482 152.482 0 0 1 20.522 17.197zM467.547 44.449c-59.261-59.262-155.69-59.27-214.96 0l-67.2 67.2c-.12.12-.25.25-.36.37-58.566 58.892-59.387 154.781.36 214.59a152.454 152.454 0 0 0 20.521 17.196c6.402 4.468 15.064 3.789 20.584-1.731l21.054-21.055c8.35-8.35 12.094-19.239 11.698-29.806a16.037 16.037 0 0 0-6.947-12.606c-2.912-2.005-6.64-4.875-10.341-8.569-28.073-28.073-28.191-73.639 0-101.83l67.2-67.19c28.239-28.239 74.3-28.069 102.325.51 27.75 28.3 26.872 73.934-1.155 101.96l-13.087 13.087c-4.35 4.35-5.769 10.79-3.783 16.612 5.864 17.194 9.042 34.999 9.69 52.721.509 13.906 17.454 20.446 27.294 10.606l37.106-37.106c59.271-59.259 59.271-155.699.001-214.959z"></path></svg>';

	jQuery(sectionSelector).find(elements.join(',')).each(function(i, el) {
		const $el = jQuery(el);
		const id = el.id;
		if (id) {
			const height = window.getComputedStyle(el).getPropertyValue('font-size');
			const icon = '<a class="header-link" href="#' + id + '" style="width:' + height + ';height:' + height + '"> ' + svg + ' </a>';
			$el.append(jQuery(icon));
		}
	});
}

style.css

.header-link {
	display: inline-block;
	margin-left: 10px;
	opacity: 0;
	transition: opacity 0.2s ease-in-out 0.1s;
	border-bottom: none !important;
	text-decoration: none !important;
}

.header-link svg {
	height: 80%;
}

h2:hover .header-link,
h3:hover .header-link,
h4:hover .header-link,
h5:hover .header-link,
h6:hover .header-link {
	opacity: 1;
}