For example you have 2 chuncks one {{recentNews}} and an other {{iLoveModx}}.
You can make a new TV (template variable) name it sideBar and select the template that you use to give it access to the TV and save it.
And then put this code in your template [*sideBar*] where you want your sidebar to show.
Now go to your site.com/manager and when you add a new page or edit a existing one.
Scroll to the bottom, thats where you will find your sideBar input field.
Now you can put in what chunk(s) you would like to display on that page {{recentNews}} or {{iLoveModx}}.
I think this is a way to do it..