Adding Harp Pedal Changes

To set up initial harp pedals, I went to the Playing Techniques section of the right panel, opened the harp pedal section, set the pedals as I wanted, and clicked Create. The pedal indications appeared above the selected measure as shown. That was fine.

A few measures later, I needed the D strings natural and the A strings sharp, so I selected those pedals; but Create is not active and will not add the new diagram.

I have used this before and don’t know what I am doing wrong.

Advice? Thanks.

Note: Some harpists don’t want the diagrams, but some do. I usually make a copy of the part with the diagrams and a copy without. Regardless of the harpist’s preference, the diagrams help me avoid making unrealistic chromatic changes.