This ahk should do it.
Compile it to exe.. maybe NewTextFile.exe.
In RegEdit go to
create a key
New Text File
under that create a key
for default value put path to 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.