[Feature] [Breakdown] Add element instances to left Elements panel

[hyuri]

In the left Elements panel, when we click on an element of a particular type, it expands and we are able to see a list of scenes the element is used in.

It would be useful to also be able to click on a scene from that list and have it expand, showing all the instances (sections of text where the element was added to) of that element in that scene. And clicking on an element instance should take us to it (line, maybe even putting the cursor on the text).