I see. So you want to show the sidebar in some pages and hide it in others. The thing is that you aren't able to choose page modules from the admin section. Adding that feature would mean hacking the core. There is no simple (or, at least, suitable for an answer here) way to that. The thing is that you can follow other simple approaches that should get you to similar results.
If you want to hide the sidebar in some pages, a layer module could help. You could use the same layer module in the FAQ plugin. Now, suppose you want to only show the side bar in the activity or faq pages. You could do this:
public function sidebar() {
if (in_array(qa_request(), array('faq', 'activity'))) {
parent::sidebar();
}
}
So, basically, you're adding a second filter apart from the one in the settings. You could add more pages or even invert the logic by negating the in_array to show the sidebar everywhere but in the faq or activity pages.