First of all, thanks for creating an awesome extension for managing translations!
I keep wondering why there are so few good localization tools out there and even the good ones usually lack one feature or the other. However, with your extension, I am very happy so far.
There is one (hopefully small) feature request I have:
Would it be possible to create secondary resx files with the <DependentUpon> tag so that they show up as sub-items to the neutral language resx? (if enabled in the configuration)
Like this (I hope the picture works):
And maybe even add a button to clean up all existing resx files in the same manner (like you did with the "Sort all files now").