In the same way the $VIRTUAL_ENV variable tells the virtual environment directory, A variable such as $VENV_NAME or $VENV_PROMPT should tell the value given to the venv `--prompt` option (Introduced in Issue22829).

An individual could override the EnvBuilder class like the docs say, but that wouldn't insure any user will have the variable set. This is crucial for usage in custom libraries that want to display the given prompt.