GroupValue: _switch == true ? _value : 0,

onChanged: (value) {
if (_switch) {
setState(() => _value = value!);
const newOffer = Mode.newOffer;
}
},
),
Center(
child: Padding(
padding: const EdgeInsets.all(8),
child: Center(
child: ButtonFabSettings<int>(
nameButton: locales.voiceSearchProfile,
listColor: buttonColors[2],
icon: SDMarketIcons.microphone,
value: 3,
groupValue: _switch == true ? _value : 0,
onChanged: (value) {
if (_switch) {
setState(() => _value = value!);
}
},
),
),
),
),
ButtonFabSettings<int>(
nameButton: locales.scannerPriceTagProfile,
listColor: buttonColors[3],
icon: Icons.verified,
value: 4,
groupValue: _switch == true ? _value : 0,
onChanged: (value) {
if (_switch) {
setState(() => _value = value!);
}
},
),
ButtonFabSettings<int>(
nameButton: locales.favoritesProfile,
listColor: buttonColors[4],
icon: Icons.star_outline,
value: 5,
groupValue: _switch == true ? _value : 0,
onChanged: (value) {
if (_switch) {
setState(() => _value = value!);
}
},
),
],
),
),
],
),
),
],
);
}
}

class ListItem {
bool isSelected;
IconData icon;
ListItem({
required this.isSelected,
required this.icon,
});
}

Ещё раз класс не нуден, у вас очень много лишнего кода ...