Extension in this case doesn't matter, Clo.
No matter if saved as a .txt file TC will decode the file according to the first 3-4 lines of header details: where the encoding type is listed.
using SUDO is not exactly the same thing (e.g., for buttons with parametric commandlines) therefore I also vote for a "run as administrator" as proposed in the first post.
Nigurrath wrote:using SUDO is not exactly the same thing (e.g., for buttons with parametric commandlines)
It is absolutely the same. Sudo just executes exact given command line via elevation. Button's context menu 'As Administrator' item does also the same thing. The only thing you should note that elevated programs don't inherit parent process environment so your environment variables will be inaccessible, and it is so for any way of starting as administrator.