What you gain
The hard boundary stays obvious. domain/ and application/ are shared, so two endpoints cannot each invent a Note. Endpoint work is local: a new feature adds presentation/notebooks/ with its own mapper, and leaves the note entity where it is.
The composition root stays one place. Screen-level or endpoint-level changes do not require a new top-level layer.
What it costs
Two rules, not one. Inner code is horizontal. Presentation is vertical. A feature is not one folder, so you still cross domain/notes and presentation/notes to follow a save.
Use cases drift into the feature folder unless you forbid it. presentation/notes/save_note_use_case.dart would look convenient and would couple the workflow to the endpoint slice.
Back to the introduction, or continue to when to use it.