background in

Button {
    // no-op
} label: {
    Label {
        Image(systemName: "chevron.down")
    } icon: {
        Text("Income")
    }
    .font(.caption.bold())
    .padding(.vertical, 10)
    .padding(.horizontal)
    .background(.white, in: Capsule()) // ←コレ！
    .foregroundColor(.black)
    .shadow(color: .black.opacity(0.05), radius: 5, x: 5, y: 5)
    .shadow(color: .black.opacity(0.03), radius: -5, x: -5, y: -5)
}