Is it normal to have an item showing when ALL video tracks are HIDDEN?

I noticed I had a text that was not appearing on the video tracks:

I have HIDEN all the video tracks I can still see it. (Its the yellow rectangle that you can see)

Even hiding the last subtitle track (so having ALL subtitles hidden), would not remove it!

There is a hidden yellow line correponding to it though, but where to access it, if it's not on the video track nor the subtitle tracks?