You can trim the start and end of a song manually, by editing the Trim values. Show the Trim Start/End columns by context-clicking on the sort column headers, then pick the Trim value you want to edit (start or end). Now, you can simply edit the value for the song, or you can play the song and pause it at the moment you want, then pick "Controls->Save Trim [Start/End] Time", and it will set the trim value for that song. Next time you go to play that song, it will start at the Trim Start time, and end at the Trim End time.
When a song has Trim values, you will see an indicator in the timeline as a red line marking the trim time.
The Trim commands in the menus are only available for the current song. You can however edit the trim values directly in the browser, and you can set multiple songs at once (to the same value).
Trim values are in CDDA timecode, that is: minutes (base 60):seconds (60):frames (74).records (4), you may edit typing timecode eg: "1:20" is one minute twenty seconds, or just "5" is five seconds, or 4:35:62.2 is 4 minutes, 35 seconds, 62 frames (62/75ths of a second) and 2 "records" (2/4 of a "frame" or 2/300ths of a second). Yeah, weird, i know.
Trimming overrides the "Auto Cue" preference (skip silence at start or end of song).
To remove a trim value, just edit the value and delete the text.