Using Node's 'Docx' to append to an existing Word doc with JS

I'm curious if it is possible to append to a generated Word document that I've created with Js and docx module. Currently I can generate the document and format it. Yet, I'm not seeing anything in their documentation about appending or adding a paragraph to an existing document (there is a section on exporting, but it always creates a new file, even if its the same name). Is this a limitation in JavaScript? I'm assuming that since I'd want to look for the document in the system files, that this creates a security issue (JS from a browser looking for a file in a end user's system) and hence why docx doesn't do it. Any guidance on this is greatly appreciated. Also, if it's not then would using Word APIs solve this?

P.S. I can share the code that generates the document, but that part is running fine, I just need to know if what I want is possible or if I'm wasting time.

This is a function I've tried and found from stackoverflow, but it was for a web app, this is a chrome extension. I've looked around and can't find anything else to try. Idally I'd like to write to the doc generated and add to it.

// pretty sure I cann't utilize a function like this unfornately
// all code is functional before this is call
function writeToDocument(doc, text){

    let paragraph = new docx.Paragraph();

    // invalid code 
    // paragraph.addRun(new docx.TextRun(text));
    // doc.addParagraph(paragraph);

    let packer = new docx.Packer();
    docx.packer.toBuffer(doc).then((buffer) =>{
        fs.writeFileSync(docName + ".docx",buffer);
    });
}

It looks this is limitation of library. There is addSection() but it is private. Also, there are no methods to open a previously generated file.

Only way is: first create content, and later create doc and save it:

let paragraphs = [];
//any way to add element to array, eg
paragraphs[paragraphs.length] = new Paragraph({
                    children: [
                        new TextRun("Hello World"),
                        new TextRun({
                            text: "Foo Bar",
                            bold: true,
                        }),
                        new TextRun({
                            text: "\tGithub is the best",
                            bold: true,
                        }),
                    ],
                });

//paragraphs[paragraphs.length] = addAnotherParagraph()


//create document
const doc = new Document({
    sections: [
        {
            properties: {},
            children: paragraphs,
        },
    ],
});

//and save it in fauvorite way

Packer.toBuffer(doc).then((buffer) => {
//why in `docx` documentation uses sync versioin?... You should avoid it
    fs.writeFileSync("My Document.docx", buffer);
});