Speaker Notes are supported by Hyperdeck. You add them with the Speaker Notes icon:

Insert presenter notes

Note

Alternatively, you can just type ;; in the editor. Here is a example of what that would look like in the editor:

;; Ask the audience to raise hands who played Mario Kart before
;; The idea is to lead from playing to the topic

# Agenda

Speaker notes are displayed in the moderator monitor below the slide preview.