Harp layout

|EDIT: I found the diatonic key layout for harp by accident, and now know how it works (manual page 20).
I can't find a way to delete this post, sorry. Below is my question, the answer is in the edited title and the manual.]

The on-screen keyboard suddenly has a non-standard layout, with three black keys per octave, coloured keys and mute keys, and a changeable note name above each group of black keys. What is this display, how did it appear, how can I get rid of it - and how can I make use of it?