Add new property to object saved in chrome.storage.local

the purpose of this function is to add data to an object saved in chrome.storage.local; I am implementing this function:

/**
 * Set object setting
 * 
 * @param {object} setting 
 */

function addSetting(setting) {
    chrome.storage.local.set({ atsu_setting: setting });
}

Then in different areas of the code I try to add more data to what already exists:

chrome.storage.local.set({ atsu_setting: {opened:false} });
chrome.storage.local.set({ atsu_setting: {url:"dato"} });

The problem is that I am monitoring the data they are saving with:

setInterval(()=>{ 
    chrome.storage.local.get(atsu)
    .then((setting) => {
        console.log(setting);
    });
}, 10000);

but this only shows me the last saved; They told me that this is because I have to obtain the information, merge it and then save it again; this implies that I must use async; therefore do this:

chrome.storage.local.set({ atsu_setting: {opened:false} });
metodo_siguiente();

You will have unwanted behavior; since the asynchronization that I know asks me to implement something like this; causing that in each memory read you need to nest code inside a.then

.then((setting) => {
     metodo_siguiente();
})

How do I resolve/improve Data Update? I am needing to read the data; save, the new ones and return this data to a variable:

Example:

function udateSetting(objeto){
    chrome.storage.local.get(atsu_setting)
    .then((setting) => {
        //validar que existe:
        if(setting){
            //agregarmos nuevos datos
            setting[Object.keys(objeto)]='dato';
            chrome.storage.local.set(setting);
            return setting;
        }
    });
}

let new_setting = udateSetting({nueva_propiedad:"dato de la propiedad"});

console.log(new_setting);