You can make a clip begin at a certain frame by using the offset function. This applies to clips loaded into the Modular Keyer via the Desk or Library node. When you link a clip loaded via the Desk or Library node into the Modular Keyer pipeline, it retains its clip controls.
For example, a slip value of -15 holds the clip at the first frame and repeats it 15 times before the clip begins. A slip value of 10 begins the clip at frame 11, since a slip value of zero corresponds to frame 1. Slip information is stored with Modular Keyer setups.