I'm playing on mouse/keyboard, and there is no button to swap to the secondary party during the portion of the story where you must traverse the Hex. Anyone know what's up?

It should be F1.

It would be nice to have that info on the store page

For what it's worth, there's an included pdf manual when you install the game on GOG Galaxy.

Also, I've put together a GOG version setup guide on Dragnier.net. Highly recommend looking it over.

https://www.dragnier.net/breath-of-fire-iv/breath-of-fire-iv-guides/breath-of-fire-iv-pc-gog-setup-guide/

I'm at this section too. Was caught completely off guard with the "Select Button" prompt. Every other key prompt before this referred to a keyboard key. I'll try the using F1.

Partially related, but not only does F1 carry the "Select" function, but F9 lets you quit the game without resorting to End Task.

I am also at this point and you need to use F1