I watched a documentary on how this telescope is going to be used with JWST. Basically the Nancy Grace telescope is a wide field high resolution telescope where they would photograph the same location in space over multiple days.

Since it’s high resolution and wide space it would still capture a huge area in detail and then they would basically use the photos taken over days/weeks to cancel out the stars/galaxies that appeared on every photo and only take the diff. That would give the anomalies like supernova, etc. and then they would focus JWST on that anomaly to zoom in and observe it closely.