can VLC really change the Thumbnail of a videoclip?

[dast]

Hi,

I would like to change the thumbnail to a videoclip, standard is the first frame, but I would prefer the last frame. So I take a snapshot and try to replace the current thumbnail with the snapshot. I go to tools -> media information -> add cover art from file and I can see the new thumbnail. But there is only one option: to close the window. In the documentation at https://www.vlchelp.com/edit-cover-album-art-picture/
it is written that "The information will be saved automatically" BUT IT IS NOT, the videoclip continue to have the old thumbnail.

There is something that I do wrong or actually VLC cannot change the thumbnail to a videoclip?

Many thanks and best regards!