For example, I created a new page, and I\'d like to use, for example, backbone.js, custom css file and some collection of images. Where should I declare all this stuff in Yii2?
From personal experience, assets are one of the parts of Yii that I found extremely frustrating.
It is hard to reliably find out where the file is going to be and the switching back and forth with debug mode on and off will create further frustration.
I suggest scrapping the asset handling and just keep all your JS files in a folder, then it can be included like this:
Yii::app()->clientScript->registerScriptFile('/js/jquery.jeditable.mini.js');