I use the Super Start add-on with Firefox (it's a "speed dial" and organizer for URLs). I have it set as the home page and the default content for new tabs. Since Firefox was updated to version 41.0, this new-tab setting has been ignored. New tabs now display Firefox's own feature, with tiles for frequently used URLs.
I've found instructions online for specifying a URL as the new-tab default (in
about:config). However, Super Start isn't a URL. It has its own setup, which includes an option to use it for new tabs:
This has worked for previous versions of Firefox. However, this setting is now ignored. (Super Start still works if you open it via its toolbar icon).
How can I manually configure Firefox 41 to use an add-on, like Super Start, as the default display for new tabs?