This extension is far from feature complete, and some things just don't work as expected. The inherited code is also a bit of a mess, and since I am no JS coder there's limits to what can be done. As this started as a very personal extension for my use, some things are the way I want them and not easily changed.

Here are some of the more common issues/bugs/TODOs and some tips:

Using Ctrl+<link key> in hints mode does not work. Using Shift+<link key> works for opening in a new tab though.
The default Ctrl+click key interferes with the common shortcut Ctrl+F for Find.
I suggest using something else for Find, like F3, or changing the key to for instance G.
Even if keys are changed, there might be conflict issues with the link hints, see below.
The extension uses a hard-coded list of link hint keys. These might interfere with common browser keys,especially if single-key shortcuts are used in the browser. If so these will need to be removed from the list.
The list of available link hint keys are in js/spatial-navigation.js:
var keys = 'abcdfghijklmnoprstuvwxyz'
You can edit this string and reload the extension. You can also add keys you want to use instead, for instance the number keys (if not used for anything else).
The CSS styles for links/hints/url display can if necessary be changed by editing the following values in js/spatial-navigation.js:
this.style.innerHTML
marker.style.cssText
display.style.cssText
There are no language options or internationalization.

Any contributions are most welcome! 🤓👍