I wanted to merge a srt (subtitle) file into a mkv video file, because vlc seems to ignore subtitle files. ChatGPT explained to me that hardcoding was an option, but this would mean the subtitle would always be visible no matter what. So I wanted to go for softcoding: This way, the subtitle is available in the mkv video file, but only visible if you want it to.
Tip: Before merging in a srt subtitle, find it in the interface (source, tracks and chapters) and set the language. I found out a Title is not needed for the subtitle track.