hiding files from folder view

Hi, here's an idea I'd like to ask for:

I'm developing a RoR application which has the normal Rails directory structure. It also uses quite a bit client-side stuff with Backbone.js which means there's another MVC structure within assets/javascript hierarchy, not to mention all the other stuff that keeps filling up the hierarchy. It also uses config/locales to do I18n, which I also need to edit sometimes. 

I love the folders view sidebar and I would actually like to use it to navigate these files. But the directory structure tends to be so crowded that jumping from one file to another from there is a chore, since opening the directory tree for some files will cause it to fill with all the other files I'm not needing and forces me to scroll back and forth. Also, with many files and folders the structure gets so wide that the visibility of what's inside of which folder gets harder to see.

Could there be (is there?) a feature to hide everything from the folders view sidebar except the directory structure (for RoR development, especially with Backbone inside assets/javascript, the directory structure IS relevant information) and files I have opened as tabs, for example? Of course, it needs to be easily toggleable when I want to open some new file...