Setting up & switching between 2 church organ sounds in Halion Sonic

For a demonstration for an organist I need a simple switch between Principal- and reed pipes. I’m using Halion Sonic. However, I’m having trouble with the setting up of the playback. How can I enter “reed pipes” in measure 1 and “switch to flute/tutti” in measure 13 in the score so that the switch is audible in Dorico? (see pics!)

As far as I know in HALion there is a Hammond C organ with drawers where you can control some 8’, 4’, 2’ registers/colors, but it sounds like a Hammond organ, and a church organ with a single immutable tutti sound.

For a fine-grained control of the pipes you need a dedicated sound library as suggested in the other thread.

Is it possible to simulate changing organ stops by having a player hold different instruments? And can a player play multiple instruments at a time?