Quick Answer: There is no reference keyboard included in Liquid Notes today. We plan to add this with one of the next updates.
Reference keyboard in the piano rollWhen clicking on the tab Piano Roll in Liquid Notes, a display of MIDI events in your arrangement becomes visible. It is is optimized for displaying single MIDI events of different instrumental tracks.
In contrast to the usual separation between single tracks, Liquid Notes represents the MIDI events of all instruments overlaid across the same visual range. Instruments can be differentiated by color. The descending order of the overlay is determined by the order of the instruments in the corresponding MIDI file.
Today those MIDI events cannot be correlated with a reference keyboard for better reading and/or identifying individual MIDI notes in Liquid Notes. Such a keyboard will be added in the near future.