How to select an input/output channel for my audio interface (Soundcraft Signature MTK12)

context.modules = [
    {   name = libpipewire-module-loopback
        args = {
            capture.props = {
                media.class = Audio/Sink
                node.name = mtk_aux_11_12
                node.description = "MTK AUX 11/12"
        audio.position = [FL FR]
            }
            playback.props = {
                node.name = "mtk_aux_11_12.output"
                node.passive = true
                target.object = "alsa_output.usb-Soundcraft_Soundcraft_Signature_12_MTK-00.pro-output-0"
        audio.position = [AUX10 AUX11]
            }
        }
    }
]