[DCP-o-matic] 'Timing' window

Hi Carl, could you explain these options to us (the Trim settings in itself is clear, although it is always worth to mention they are offsets FROM the Start and FROM the end)? I know the 'Keep video in sequence' belongs to the content/timeline box above the Timing options, but still, what does it mean? And, a long time want to have - cue to any position with the play slider below the preview image, then hit a key or 'Set' button to input the current cue time below the slider into the Trim number boxes. Why do we have these 'SET' buttons anyway? What has become of the DVD-o-matic alternative options 'PlayTrim/EncodeTrim'? - Carsten