The Reset Subtitles command can be started from Titles/Reset Subtitles.
It allows you to change the subtitles attributes like color, horizontal and vertical position, presentation effects and colors to their default values specified in the Subtitles page of the Project Settings:
Reset Subtitles
Include both subtitle tracks - the option will be displayed only when the project contains subtitles in the Main and Secondary tracks. Respectively, after activating it subtitles from both the Main and Secondary tracks will be affected simultaneously.