By pressing Shift+G on an appropriate window the current position of the timeline can be adjusted to any position entered into either the 'Enter New Sequence Position' or 'Enter new Media Preview position' dialogs. Enter a new position within the duration of the timeline and click OK to go to that position.

From the 'Adjust your slide' dialog while adjusting images, pressing Shift+G will allow you to modify the slide duration. Enter a new duration for your slide and click Apply to save the change.

From the 'Adjust your slide' dialog while adjusting videos, clicking either the 'In Point:' or 'Out Point:' field controls will open the 'Enter New In Point dialog' or 'Enter New Out Point dialog' respectively. Once either of these dialogs is open, enter a new in or out point into the field and click Apply to save the change.

Note that this method of editing slide lengths is best when precise lengths have been predetermined. If you prefer to line your in and out points up to visual cues on the slide, use the slide navigation buttons to cue up the precise moment you would like to change the in or out point to, then use the red and blue flags to set each point to the desired position.