Problem with synchronizing MGRT template settings

I created a subtitle template in MGRT format. I want to apply changes to all the subtitles in my video at once (font, outline color, text size). I can’t find this option, and I can’t export it as an MGRT template either—that option is disabled. How can I apply these changes to all MGRT subtitles on the timeline at once? I have a 2-minute video, and it’s impossible to edit each subtitle individually.