Good question, difficult to answer. I'm afraid default filename for New context menu is hardcoded in
shell32.dll: by default, the name of the new file you create is the name of the file type, preceded by the word New and followed by the appropriate filename extension.
I can't verify promising combination of
ItemName values under the
ShellNew subkey (read more here).
The last chance seems to be the
command subkey method: if contains something like
wscript.exe "full-path\ItemName.vbs" "%1"
ItemName.vbs could create arbitrary named file, deriving it from the
"%1": it is fully qualified path to default file name.
The script could e.g. copy a template file from the
FileName value; if the name of template file is not fully qualified there, then the script could search for it in the same way as though using
FileName value method (read more here).
Above mentioned this registry subkey:
.abc epitomizes any desired file extension...
--- Note ---
In a registry editor, navigate to
HKEY_CLASSES_ROOT\.html and take note of of the
Default value data could be something like
ChromeHTML. Now, navigate to
HKEY_CLASSES_ROOT\ChromeHTML and take note of of the
Default value data again: could be something like
Chrome HTML Document.
In that scenario, the New context menu should offer
Chrome HTML Document with default filename
New Chrome HTML Document.html.
(By the way, clean Windows default above to
HTML Document and
New HTML Document.html, respectively).
Back to our occurrence:
New is hardcoded in
Chrome HTML Document is data from registry (could be changed) and
.html is our filename extension (filetype).
However, I'd feel happy for the brief, short New prefix: in my localization defauts it to Nový objekt - (hyphen including!)