It's very far from ideal, but until someone posts a GUI option, you can remove the end of a video with:
That will copy everything in the file up until 15 minutes, 32 seconds. Obviously, figure out when you want the video to end. You can similarly use the -ss option to cut off the beginning of a video:
avconv -i input.avi -c copy -t 00:15:32 output.avi
This will begin copying at 3 minutes 30 seconds, for a length of 5 minutes 20 seconds.
avconv -i input.avi -c copy -ss 00:03:30 -t 00:05:20 output.avi
The best NLE I used on Linux, back when I was trying out the options a few years ago, was Cinelerra. I don't know if it can do what you want, though, and it's not available in the repos - you can install it from this PPA, and find out for yourself if it'll suit your needs.