I see, a global setting.
Aside from copying your modified .skn file to each of the
other project's
...\!SkinSubFolder!\Skinname directories, I'm not sure what
else you can try.
I suppose you could go into each of the other projects and
then import your modified .skn file, then have the project use
that.
That would still leave you opening each project individually
and making the change, though, without a built-in global solution
to apply it to all of your projects.