Exposure exposes (heh) three events to KubeJS:
ExposureEvents.addEntityInFrameExtraData- can be used to add additional properties to frame's entity in frame extra data
ExposureEvents.modifyFrameExtraData - can be used to add additional properties to frame's extra data
ExposureEvents.frameAdded - somewhat similar to FrameExposedTrigger
ProbeJS can greatly help with KubeJS scripts. It'll show all methods that are available in the above events.