Install new MS Win10 Language-dialect Voice packs via standard Win10
Settings > Time & Language > Speech > Manage voices > [+]Add voices
This will add physical Voice data files in subdirectories below this directory:
Code:
C:\Windows\Speech_OneCore\Engines\TTS\
All Voices for a given Language-dialect (e.g. en-GB, en-US etc.) are stored in the same subdirectory. Each MS Voice consists of several physical files.