The "Play a Random Sound" action parses tokens for both the "Play a random sound from a selection list" and "Play a random sound from a directory" options.
The former has a tooltip for the file path field in the "Add Random Sound Files"/"Edit a Random Sound File" dialog noting this capability, the latter has no tooltip(at all), neither have this feature mentioned in VoiceAttackHelp.pdf
EDIT: "Play a Sound" documentation now notes token capability (v1.7.8+, possibly earlier)