I used to love this add-on, until I found out that it doesn't work on Firefox 52 ESR (which I have to use at work, as it has Windows Vista installed, not upgradable). At home, I still used it, until I discovered a fork of it, "Switch Container Plus", which is much bigger in size (34kB against 15kB), but also has a better functionality (for example, SCP works on "new tabs", while SC never did).