It’s good to learn how to install extensions and plugins but keep in mind, this one will do nothing to sort out the problem you were having with the molding.
In a similar problem, if you can’t see geometry that is hidden within a group, but you don’t know which group it is: Use the Outliner tab and go through all the groups- open each one of the (+) boxes. Eventually you should find a group where the inner group name is italicized and grey. Click on that and it should open up a bounding box that appears empty. Inside the model, click ‘unhide’ that should reveal what’s been hidden.