AI suggests this, with the caution that the info may not be 100% accurate...
"Regarding burning DVDs with two types of subtitles using VideoPad:
VideoPad supports projects with multiple subtitle tracks and multiple audio tracks, which means you can have more than one subtitle track in your project.
However, for burning DVDs specifically, VideoPad itself does not provide a separate DVD authoring interface inside the editor. Instead, it allows exporting the video with subtitles burned in or exporting a video file with subtitles.
Use VideoPad Video Editor to create and manage multiple subtitle tracks. VideoPad allows importing, editing, and exporting multiple subtitles in formats like SRT, and these can be embedded in your video project.
While you can author multiple subtitle tracks in VideoPad, the DVD menu created in Express Burn, for example, cannot control subtitle track selection. This means multi-subtitle DVDs with menu selection functionality are not fully supported within the NCH suite at this time."
Suggestions can be filed here.