Add the typewriter effect to the subtitle
Add the typewriter effect to the subtitle to get this effect:
Adding the typewriter effect on a subtilte is not possible:
Titles and subtitles work completely different under the hood. While titles are XML that is treated as producer, subtitles are applied via the avfilter.subtitles effect internally (https://www.mltframework.org/plugins/FilterAvfilter-subtitles/).