So I tried the add on because of the ability to prevent unloaded tabs to load, I understand that there is no APIs yet, but it does not works as I expected. May I suggest that you take a look at Tab Suspender addon? the way the developer implemented this functionality is way better in my opinion, sadly I can not use this addon due to incompatibilities with other, more crucial, extensions.

Lastly, event do some functions are working in underoptimal conditions, I would have rated it four stars if it was not because it lacks an, in my opinion, key feacture. It can't auto unload tabs.

Link: https://add0n.com/tab-suspender.html