My firestore structure

Subwork Package (collection)
        - UID (document)
                - Subwork Registration (subcollection)
                        - Doc unique ID (document)
                                - data etc etc
        - UID (document)

I have a table that displays all the documents that I have, inside the "Subwork Registration" subcollection.

//LOAD DATA TO TABLE IS SUCCESS
initializeTable() {
    this.SubworkTable = [];
    firestore
        .collectionGroup("Subwork Registration")
        .get()
        .then(querySnapshot => {
            querySnapshot.forEach(doc => {
                this.SubworkTable.push({ ...doc.data(), id: doc.id })
            })
        })
}

Then, I will pick one of the docs and edit/update its content from the list of docs that shows on the table. But when I do as below, I got into an error .collectionGroup("").doc("") is not a function kind of error

data: () => ({
    editedItem: {
        v-model: '',
        v-model: '',
        // etc etc
   }
})

//METHODS: {}
UpdateTable() {
    var data = {
        //
    };
    firestore
        .collectionGroup("Subwork Registration")
        .doc(this.editedItem.id)
        .update(data)
        .then(() => {
            //
        })

}

I do take note that we cannot update or set if we do .collectionGroup("Subwork Registration").doc() but Im not sure how to do it the right way (to edit/update document inside a subcollection).

Any advice?