Hello,
I'm not sure if I understood completely the issue if you want to avoid or detect the CAP, NUM and SCROLL.
Assuming you are using the demo for the hid_device... by any chance have you checked how it's implemented the different events for the mouse and how those are reported? I believe that can help you.
Also, you can get a general overview of how are both the host and device implemented by checking the BLE Demo Applications User's Guide.
Regards,
Estephania