Once an instrument is loaded, how can I switch presets from a list?

You were right, it is the preset list if the presets are instruments and not snapshots, but the idea of Quickload is you get to choose which libraries’ presets show in that list

I think it’s confusing because NI use the terms ‘instrument’ and ‘preset’ loosely and sometimes interchangeably. Snapshots are a more recent concept that enable sub presets to be created for each instrument. But a whole library like the Factory library and Hypha may contain hundreds of instruments, it’s those you can browse from that drop-down but they are all presets essentially, just at different levels