To make Notepad files always open in a new or separate window in Windows 11, open Notepad setting and change the 'Opening files' option.

A CSV file is a simple text file that you can open in a wide variety of programs, including any program that works with plain text like the Notepad app.

Otherwise, Windows will continue to open files with its built-in File Explorer instead of the third-party app you installed.

In reality, though, when you double-click on it, it would instead open in Notepad because its true, but not visible, extension is actually .txt, which corresponds to a text file.