How to add a mark "horizontal playback"

When an MP4 file recorded at 1920X1080 is played vertically on a mobile phone, how is the “horizontal playback” mark in the lower right corner made and added to the MP4 file?

I am sure this is a function of your mobile phone. It know the dimensions of the video file and of course of its display and if that is different it displays the icon.

No,mobile phone has not the function! If you record horizontal a MP4 file used your mobile phone, then vertical playback this vedio at your phone. it will not show the MARK

Well, perhaps that’s the case. Still, the icon shows up in the status or tool bar of the player app and not in the video (it would be somewhere in the lower right-hand corner in the blue area of the video).

What does this have to do with Kdenlive?