You or someone else might need to port the add-on from using a URL bar button to a regular button. It might be as simple as changing page_action to browser_action in the manifest.json file (https://github.com/jscher2000/cache-favicons-for-bookmarks-extension/blob/master/manifest.json) but I haven't tested it. (**EDIT** the "show_matches" key isn't supported for browser_action, so that would need to be removed.)

I think it's possible to provide the option of having either a regular toolbar button ("browser action") or an address bar button ("page action") but unfortunately, there's no way to move it, it would need to be changed through the Options page (after writing all the new code).

Do you have a suggestion for a new icon? You can send it to me at jscher2000@outlook.com, or create a new issue at https://github.com/jscher2000/cache-favicons-for-bookmarks-extension/issues