N-Panel is basically a control center of the whole operation. From here you apply changes, restore copies, create graph and element snapshots.
Build from Graph - is a main function that takes edits on your graph, evaluates it against original scene and applies this changes to an Outliner.
Build from Outliner - currently it’s only purpose is to create the base nodes (Scene & Scene Root) for currently opened scene. You can open the graph, press the button, switch the scene press the button again and it’ll create new base nodes in the same graph.
Multi-Shot Mode - Blender’s collections for all scenes live in a single global <data.collections> property, which means you can’t have 2 collections named the same way. Multi-shot Mode makes sure that when you create collections they automatically have appended suffix with your scene name. For example: you create collection geo, in scene sc1 this collection will become geo_sc1, in scene sc2 it’ll become geo_sc2, etc.
Convert Existing Single-Shot - in case if you already have a shot structure built, but want to have multi-shot workflow you can convert existing single-shot to multi-shot. It’ll run through the opened scene and appends the scene suffix to all collections.