If i use the speech recognition feature to create subtitles, the subtitle track remains in the timeline when I have finished.
If I want to create subtitles for another clip, I have to close kdenlive and then start it again.
Is there another way?

Not sure what you mean. You can close the subtitle track by clicking click on the subtitle icon: https://docs.kdenlive.org/en/effects_an ... l#subtitle. To create additional subtitle just double click into the subtitle track.