While in a text input area, when a Bluetooth keyboard is connected to a IOS device and the On Screen Keyboard is "hidden", is there a way to start SIRIs dictation function? (Besides activating the On Screen Keyboard and click on the microphone button)

I am creating a BLE HID keyboard based on a Nordic nRF52840 chip. I can send most keys just fine. But sending the HID Keyboard code PAGE_UP / PAGE_DOWN / HOME / END is not working. On other commercial keyboard these key are "send" in combinations of the Fn key and the ARROW keys. Can anyone tell me how to "send" these keys to IOS? Or how to send the "Fn key" so that I can send the arrow keys thereafter.