Step-1:-

Install Required library

npm i react-native-searchable-dropdown

Step-2

Create MockDB

export const Data=[
    {
        id:1,
        name:'Milk'
    },
    {
        id:2,
        name:'Coffee'
    },
    {
        id:3,
        name:'Tea'
    },
    ................ ]

Step-3:-

Here I am going to create list of data which woill add in a array through filter Search Bar

const TaskScreen = () => {

    const [listData, setListData] = useState([]);

    const listDataRender = ({ item }) => {
        return (
            <View style={styles.list}>

                <Text>{item.name}</Text>
            </View>
        )
    }


    const addHandler = (name) => {
        setListData(currentGoals => [
            ...currentGoals,
            { id: Math.random(), name: name }
        ]);

    };

Step-4:-

Create dropdown

   <SearchableDropdown

                    textInputProps={
                        {
                            placeholder: 'Search',


                            style: {
                                padding: 10,
                                borderWidth: 1,
                                borderColor: '#ccc',

                                color: 'black',
                                height: 40,
                                width: 300
                            },
                        }
                    }
                    containerStyle={{ padding: 5 }}

                    itemStyle={{
                        padding: 10,
                        marginTop: 2,
                        backgroundColor: '#ddd',
                        borderColor: '#bbb',
                        borderWidth: 1,
                        borderRadius: 5,
                    }}
                    itemTextStyle={{ color: '#222' }}
                    itemsContainerStyle={{ maxHeight: 140 }}
                    items={Data}
                    onItemSelect={(item) => {
                        addHandler(item.name)

                    }}
                    listProps={
                        {
                            nestedScrollEnabled: true,
                        }
                    }

                />

Step-5

Add + Button

 <TouchableOpacity

                    onPress={() => {
                     let index= Math.floor(Math.random() * Data.length);
                        let name= Data[index].name;
                        addHandler(name);
                    }
                    }

                    style={styles.addButton}>
                    <Text style={{ textAlign: 'center' }}>+</Text>
                </TouchableOpacity>

Now You are Done !!!

Output