"collapse all" all nodes in one click in firefox or chrome
To collapse all XML nodes in Chrome, execute this in your JavaScript console
var nodes = document.getElementsByClassName("button collapse-button");for (var i = 0; i < nodes.length; i++) { nodes[i].click();}
If firefox or chrome are not a strict requirement, I suggest geany, in particular its pretty-printer plugin.With it you can simply format the file in a human-friendly way, fold and un-fold all elements in a single click and so on.
If you are on debian or ubuntu:
sudo apt-get install geany geany-plugin-prettyprinter