I add multiple video clips to my timeline. I add a text filter to some of them. I copy paste text filter onto a clip. Suddenly the copied text is now shown as well on every clip in the timeline. I delete this filter. The text remains. I delete the clips. The text remains. I delete the video track. The text remains.
Maybe you applied it to the timeline as well.
Click the timeline head and check.
Thank you for your reply. It was exactly this. I had no idea the blank space next to the timeline was actually something.