With so many different skin xml's floating around, it is hard to know if the skin you are working on is maybe missing elements you'd like to be aware of.
My own active skinning days are probably mostly over, but this part has often been a big and very time consuming challenge for me.
To help with that I created an excel sheet with some macros in it, and now streamlined it for some possible public use.
You can paste the (messy) content of two different xml's in it, and get a cleaned-up result with a good overview and comparison of possible missing elements, duplicate entries, and even differences in rgb coloring attributes.
A 'master sheet' is pre-loaded. You can match your xml against that one.
You could also copy resulting cleaned-up output to e.g. notepad++ and use it's features like it's 'compare' plugin.
This all should be helpful to get a fast and manageable way to view and handle possible problems and missing elements.
Prerequisites are some minor Excel knowledge and the use of notepad++ and probably it's 'compare' function.
The work sheet contains a tab with a quick guide.
It was meant for personal use, so it might still be a little buggy and unsophisticated, but I thought to share it since it might be helpful to others too.
Testers welcome, suggestions for improvement welcome, copy the good bits and create and publish your own improved version is also fine by me.
As I mentioned, there is a 'master sheet' pre-loaded in the sheet. It's objective is to be complete, correct and up-to-date. (it probably isn't though)
Feel free to respond here if you find any errors or omissions in it.

edit:
project is closed
too much effort to maintain