Hi,
It isn't possible at the moment with the video widget. A way to do it (not pretty and a bit complicated) would be to adapt the seek_to_frame (requested next frame number) to have it look for the number of the last frame first and then go down.
What is the use case ? Potentially could be added in the future but we don't really see the use as of now :grinning_face_with_sweat:.
/Romain
