BLE HID of STM32WB55 integrated send volume up key

[SLin.3]

Hello

I'm developing a project on chip STM32WB55. I have referenced the demo about

BLE-HID of ST's "STM32Cube_FW_WB_V1.16.0". The sample code looks define for mouse usage. Could anyone can teach me how to integrated send volume up key into this sample code (BLE_HID) ?