Mozart wrote the beautiful Concerto for Flute & Harp K.266 for the Duc de Guines and his talented daughter, despite being not particularly fond of either the flute or the harp!
This Andante has been adapted [and a cadenza added] for performance without orchestra, and all editorial markings are specifically for harpists.
However, the part may be easily performed on the piano by ignoring the editorial markings and adding some discrete pedalling wherever appropriate.