The sample editor is currently a rather abstract idea for sample manipulation, compositing, recording, and transformation functionalites for the platform. The initial plan is to add capabilities to the [midi-editor] for notes to be samples in addition to MIDI notes. Playback is implemented via an [audio-worklet-processor] that schedules and plays back samples according to timings from the [global-beat-counter].
There is a legacy sample recorder built into the [granular-synthesizer], but plans are to remove it from there and make it a part of the sample recorder module. It's possible that it will end up getting wrapped with a dedicated [patch-network] node as well for simple recording + export use cases.
As of the time of writing this, the sample editor is still not really in existence. It's possible that it will take on some other form later.