This syntax works for default.pa, nf and system.pa, even if the latter makes no sense as a user configuration file. User client configuration file example ~/.config/pulse/nf.
For simple changes the latter is preferred because the user will not be required to update the file when system-wide defaults change.
This can be done either by copying the system file under /etc/pulse to the user's configuration directory, or by creating a new file that includes it with the syntax. For the examples below which modify the user's configuration file it may be necessary to first create the file. System-wide configuration files are located under /etc/pulse while user configuration files are located under $XDG_CONFIG_HOME/pulse, which defaults to ~/.config/pulse.