Mine does the same garbage. Never had an issue with my LG phones with video editing. LG also had full screen 3D live video wallpapers. Plus a better camera, full drop protection built in, a removable battery and then some. I hate samsung, the curved screen is a joke.
It pretty bad when people cant crop a video and have to search the internet for the stupid note 9. I hate you samsung. This is easy stuff.
It saves it as a new video, sometimes in a separate folder probably called something like "video editor". Annoying thing is if you edit a video it will save the new one with whatever time and date it is when you edit it not when the original one was taken and I assume it does the same with location.
You have to touch, hold, and drag the black bars with the white line on either end to where You want the video to begin & end.
I thought the orange arrow was the way, too!
Leave it to the ***** at Samsung to remove a perfectly good app/feature, namely their video editor. Pro tip Samsung: the name of the game is adding and improving features, not removing them/making them worse.