That "Cut" option you see is meant to choose a transition when entering or existing a video Part. Cut is the default transition option where there is no fading between video Parts.
At this time, Twinmotion doesn't have an option that would let you edit a video so that you can skip any part of the video. You would need to the edit the video Part by expanding it, then adjusting the final keyframe to the position you want to end in and reducing the Part length by one second to achieve your desired effect.
Let me know if that helps, or if any part of that explanation was unclear.
Thanks for all those informations. It clearly appears right now that the cizor is not to cut, I thought TM was able to edit video after watching tutorials but it seems it wasn't about to cut but only to set a sequences order... I'm working in After effect with of course longer sequences than what I finally use. So, when it's time to get the final render... shorter is better. I'll try the trick you told me.