I have managed to try it now, and indeed it is almost perfect for my use case :
Often I find videos on youtube for example which I want to show snippet to someone or save it. So I download it easily with youtube-dl but then clipping is never really easy (especially on linux).
To improve the tool it would be nice to play the part clipped with the sound to check if it's ok. Also the tool failed to load one video.
Good job !