Seems great but for one minor issue Rated 5 out of 5 stars
This add-on seems great. Originally I thought sites would have to be entered one at a time, which would be a bit of a pain. However, it turns out you can drag and drop a bookmarks folder right into the list of sites for a group, which is great.
The only issue I've found is that when a lockdown is in place for one or more groups, it is impossible to begin a lockdown on other groups. You have to first manually end the current lockdown. (Of course, if a person has the various blocks in place to prevent them doing that, then it would be completely impossible.) It should be possible to add groups to lockdown and/or extend the lockdown for the current group while it is in effect. (Of course, I can see how this will be a bit of a coding challenge to not allow the lockdown to be shortened with this method, or groups to be removed. But certainly surmountable, and necessary!)