I'm not at my computer for reference now, but could be the photobooth in RC is loaded using level template. If you wish to edit it but can't target specific items, it sounds like you may want to try and right click > Explode level. It's not as dangerous as it may sound :') It basically "tears apart" level templates back into editable mode.
Not that I've dabbled much with portraits at the moment, if that's even the right way to do it to fix your problem; No idea. But I do believe level templates inherits its content from a source level. So if you click on the booth, check in the sidebar what it says on "Level Name" and load a new level, find the level in the browser and pull up that, then what ever changes you make there 'should' (if I haven't misunderstood) transfer over to existing maps that are pulling from that level template too.
Glad you figured it out!
Last edited by The Composer; 13/10/17 01:25 AM.