There are two ways to change the pitch of a note by semitones using the Score Editor. The first is to select the note (by double-clicking, control-clicking or dragging the mouse) and then choosing Transpose from the Edit menu. The second is to choose the NS tool, select the note to be transposed by clicking and holding down the mouse over the note, and then, instead of dragging the note up and down with the mouse, which moves the note in key, press the Up or Down arrow keys. Do not try to transpose a note by selecting the note and choosing Enharmonic Spelling from the Edit menu - this will only change the enharmonic spelling of the selected note. You can also change the pitch of a note by semitones using the NS tool in the Piano Roll Editor.