Can't change instruments in Garageband 10.2 (Mac)

I remember in 10.1 I used to be able to click on the instrument then choose from folders, but now I just a window pop-up with icons, and hovering over them doesn't tell me what they are. Also there seemed to be dozens more, now it just looks like the same selection as what was on my iPad 4 last year (very limited).

Clicking them changes the icon of the instrument on the track but doesn't change any of the existing notes to that instrument.

What am I missing here?