There is no need
The SaveAs window will default to showing
.txt in the file type drop-down, but if a type is given as part of the filename, it will use that instead.
For example, if you create a new file and name it
newfile.zzz, open it with Np++ and then choose
SaveAs... it will appear as:
File name: newfile.zzz
Save as type: Normal text file (*.txt)
However, if you just click the
Save button at this point, the file will be saved as just
newfile.zzz and not
If you don't want .txt appearing in the type
Default Directory tick "Use new style save dialog" and it will default to showing
all types (*.*) when you go to save.
Adding a language
If the language exists as one that notepad knows about, but with a unique file extension, then you can add that extension in the style configurator.
Select your language and add your extension at the bottom, in the
User ext box.
If Notepad++ doesn't know about your language, then you can add one:
Define your language
The minimum amount you need to do is
Save As, set your language name, then set the file extension you want.
This may help, but I haven't tested it.