How can I add an item to the 'new' context menu?

One more thing:

If you want to add a file as a template for the new item, use

Windows Registry Editor Version 5.00
[HKEY_CLASSES_ROOT\.html\ShellNew]
"FileName"="html.html"

and then place the file (html.html) in:

• For your own profile: %Userprofile%\Templates
• For all users: %Allusersprofile%\Templates
• For the whole system: %Systemroot%\ShellNew

One more detail: if you want to delete the "Windows Live Call" entry, use:

[-HKEY_CLASSES_ROOT\.wlcshrtctv2\LiveCall\ShellNew]

To add extensions of your choice to the list: create a file, add the content below, save it as whatever.reg, and run it.

Note: Replace .png with the file extension you want to add and replace whatever with anything you want.

Windows Registry Editor Version 5.00

[HKEY_CLASSES_ROOT\.png\ShellNew]
"NullFile"=""

Source

Go in to registry editor and expand HKEY_CLASSES_ROOT

Go to .file_extention

and create a key called ShellNew

Inside that, create a new string key called NullFile with no value

For example, if I wanted to create a new entry for a blank .wil object* I would create

[HKEY_CLASSES_ROOT\.wil\ShellNew]
NullFile = ""

*if the file extension such as .wil does not exist, I would first create a file with that extension and double click it. Open it with the program of my choice as this would then create the other needed registry keys and make your job easier.

ShellNewHandler helped me to restore my Windows 7 shell menu > New > txt document entry.

1. Uncheck .txt
2. Click Apply
3. Check .txt
4. Click Apply

It seems that the other solutions here are outdated. At least none of these worked for me in Windows 10 v. 1709 Build 16299.192 (Edit: still works in version 1809). I did some testing in a VM and this is what works in Windows 10 1709, as of 2018.01.12:

Add the registry file:

Create a new registry file file with the following content:

Windows Registry Editor Version 5.00

; new file type
[HKEY_CLASSES_ROOT\.xyz]
@="xyz"

; template
[HKEY_CLASSES_ROOT\.xyz\ShellNew]
"FileName"=""

; file type name
[HKEY_CLASSES_ROOT\xyz]
@="XYZ test file"

Replace xyz with the extension you would like to add. And replace XYZ test file with the name of the file extension (e.g a .scss file would be "syntactically awesome style sheet file”). If you want to use a template file see the explanation below.

It might be necessary to restart Windows Explorer after you have added the registry file. You can restart explorer.exe by typing the following in CMD:

taskkill /f /im explorer.exe & start explorer.exe

Explanation of the code:

[HKEY_CLASSES_ROOT\.xyz]
@="xyz"

Will create a new file type in the registry.

[HKEY_CLASSES_ROOT\.xyz\ShellNew]
"FileName"=""

This will enable you to use a template for all new files of this file format. We could for example write "template.xyz" and make a new file called “template.xyz” and use it a s a template. So each time you make a new file it will be populated with pre-made content. As Eduardo Molteni mentioned the paths for the template files are: %Userprofile%\Templates, %Allusersprofile%\Templates or for the whole system %Systemroot%\ShellNew. In this example we haven’t specified any template name because we don’t want to use any.

[HKEY_CLASSES_ROOT\xyz]
@="XYZ test file"

This will be the name of the file type both for the context menu and the newly created files. As far as I know leaving this value blank does not work.

Icon:

The icon is added once Windows have associated a software with the file type.