I want every video to have the album art thumbnail so I can always visually identify them regardless of yhr filename but it seems like MP4s dont want to do that

I dont need like ALL/every video file necessarily to have it but I do need a way to be able to do it arbitrarily where I want to be able to identify the video and the thumnail is just black othewise. I imagine i might need to make the very first frame that image if the thumbnail approach is a no-go unlike with FLAC, or MP3s or other media formats that empirically support it

A few apps I use like to make the videos nameless and without a thumbnail it can be too messy and duplicative so I need to ensure I can always see at first glance what is what