Trimming footage in Kino is easier than in any editor I've used. Assume you have loaded one long clip, five minutes of video, all in one scene. In Edit mode, find what you want trimmed, and cut it. The first 30 seconds are bad? No problem play the clip to the point you want to begin. Click the icon to split the scene. Click back up one frame so that the head is positioned on the last frame of the first 30 seconds. Click on the scissors. It's gone.
Want to take out 50 frames later on? Split the clip at the start and the end of the section you want to lose. Position the head over that section. Click on the scissors. It's gone.
Trimming frames this way is very fast, very simple. Make a mistake and cut the wrong scene? Click Undo.