Is KEY_LEFTALT + KEY_LEFT not supported?

[jclsn]

I am trying to explicitely map the side buttons to Alt+left and Alt+right. This way I could keep the browser navigation functionality and also map these key combinations to other applications. It doesn't seem to work though. When I exchanged KEY_LEFTALT with KEY_LEFTMETA it works.

devices: ({
    name: "Wireless Mouse MX Master 3";

    buttons: (

        {
            # Thumb "Back" button → Send Alt Left + Left
            cid = 0x53;
            mode: "OnPress";
            action = 
            {
                type: "Keypress";
                keys = ["KEY_LEFTALT", "KEY_LEFT"];
            }
        },
        {
            # Thumb "Forward" button → Send Alt Left + Right
            cid = 0x56;
            mode: "OnPress";
            action = 
            {
                type: "Keypress";
                keys = ["KEY_LEFTALT", "KEY_RIGHT"];
            },
        }
        );
});