Hi Rachel, You can make this work by adding the engraver to the staff you want it to print above (in this case the harp's upper staff). Based on your example the code might look something like this:
\new Staff \with {
\consists Mark_engraver
\consists Metronome_mark_engraver
} {
\tempo "Adagio"
\Treble
}
Hope that helps,
Kevin
