Eu preciso responder à minha própria pergunta nos comentários.
Para editar a seção privada, ela deve ser carregada antes.
Para o Visual Studio, pode ser feito desta forma:
link
The increase the isolation and resilience of VS 2017, it uses now a
private registry hive. Internally VS uses a redirection and while for
VS extensions (which are dlls) this is transparent, for external
processes (that are exes), this causes them not to work.
To change values in the private registry hive by hand, you can use
regedit.exe to load a private hive. You need to select the HKEY_USERS
node, and click the File > Load Hive… menu. You select the
privateregistry.bin file, give a name to the hive (I entered
“VS2017PrivateRegistry”) and now you can see the 15.0_Config key
populated as usual (note: use File > Unload Hive when done):
To change values in the private registry hive programmatically you
need either to build an extension for VS or if you want to use an
external exe you need to use the RegLoadAppKey function or avoid using
the registry directly and use the External Settings Manager. See the
section “Change: Reduce registry impact” in Breaking Changes in Visual
Studio 2017 extensibility.
Não se esqueça de descarregar a seção no regedit antes de iniciar a aplicação usando-a.