In flutter How to add a list to another list, how to delete, and recall the data? - flutter

Question

To make my question clear:
I work in meals page layout and the idea is the user will select the food item of his/her meal from a list by click on a checkbox, and after that add meal in the system.
Question is:
I need to create a list (growth list) that contains all the food item information that the user is select it and after the user is press "add" button I will save each single food item' information from list to the database. I try to match ways but it not work. and I don't understand the wrong. I try a list and the problem is was how to callback the single food item's information. After that, now I try nested list and the problem is was how to insert or add the food item's information to a list.
here a code of nested list:
List<List> food= [];
add when click on checkbox:
List foo=[widget.id,widget.name,widget.carbs,widget.Amunt];
//when try with insert:
food.insert(index, foo);
//when try with add:
food[index].add(foo);
remove:
food.removeAt(index);
callback:
for(int i=0;i<food.length;i++){
Item vat= Item(food[i][0],mealId, dbEmail,food[i][1], food[i][2], food[i][3]);
var dbItem= await helper.insertFood(Item);
}
here an old code of list:
List food;
add when click on checkbox:
List foo=[widget.id,widget.name,widget.carbs,widget.Amunt];
varty.add({ 'id':widget.id,'name':widget.name,'carb':widget.carbs,'amunt':widget.Amunt});
remove:
food.removeAt(index);
callback:
for(int i=0;i<food.length;i++){
Item vat= Item(food[i]['id'],mealId,dbEmail,food[i]['name'],food[i]['carb'],food[i]['amunt']);
var dbItem= await helper.insertFood(Item);
}
I think there's something I didn't use the right way but I don't know what it is!
So, I would be grateful for any help.