this is a copy of https://kinsta.com/blog/anchor-links/#anchor-links-wordpress-plugin
After you’ve installed and activated the plugin, go into your post and create a hyperlink on your anchor text. Instead of linking it to a URL, post, or page; you will assign it an anchor name with a # before it.
Add anchor name
Highlight the header you want to link it up to. Then click on “Insert” from the button at the top and select “Anchor.” This button shows up in the editor because of the TinyMCE Advanced plugin.
Input the anchor name you gave it in Step 1 and click “OK.” This plugin saves you time because you never have to leave the visual editor view. If you’re doing it manually with HTML you have to bounce between both the visual editor and text editor (HTML) views.