Logi Options+ should allow users to rebind other shortcuts than just a few special keys. On my k380 I can only rebind 4 keys. But I'd like to rebind fn-up/down to be page-up/down, rather than brightness, which is a longstanding issue with this keyboard. Apple documents that fn-up/down should be page-up/down 1. Please let us set this correct behaviour through the user interface.