How do I write macros for a game mouse?

I have a ComsicByte Pulsar V2 that is a mouse for games. I am trying to configure one of the buttons for the letter G (G for grenade) but no option allows me to assign keyboard keys to a mouse button.

The only option that allows me to do something customized is the "macro" option. But nothing appears in this option and I have no idea how to proceed.

I have included two images for further understanding and any help in this regard would be appreciated.

Primary image

Macro option

PS: I'm new here, so I'm not sure if this is the right question; please correct me if necessary.