This ahk should do it.
Sendmode,input
Click,Right
Send,w
Sleep,200
Send,t
Compile it to exe.. maybe NewTextFile.exe.
In RegEdit go to
HKEY_CLASSES_ROOT\Directory\shell
create a key
New Text File
under that create a key
command
for default value put path to NewTextFile.exe
example C:\Utils\NewTextFile.exe
Since there is no window it should not block the mouse. It's just a macro to right click to open menu, then sends 'w' and then 't' the system does the rest. It's just opening the New submenu.