In a GNOME extension settings window, how do I stretch a text field to take the whole row?

I am working on this extension and for the settings window, I would like the text field where users type their message to take the whole row. Right now, it takes half of it because of the space for a label.

Also, how would I do it in both gtk4 and gtk3?

Thanks for any help!

'use strict';

//Import required libraries
const { Gio, GObject, Gtk } = imports.gi;
const ExtensionUtils = imports.misc.extensionUtils;//Access to settings from schema

function init() {}


//GTK4 WINDOW

//Dectect Gnome Version Number
const Config = imports.misc.config;
const [major, minor] = Config.PACKAGE_VERSION.split('.').map(s => Number(s));

function fillPreferencesWindow(window) {
    if (major >= 42) {//Check for Gnome 42 or above
        const Adw = imports.gi.Adw;

        //Create a preferences page and group
        const page = new Adw.PreferencesPage();
        window.add(page);
        const group = new Adw.PreferencesGroup({ title: 'Write your message' });
        page.add(group);

        let settings = ExtensionUtils.getSettings();

        //Add the row for the text entry
        const messageRow = new Adw.ActionRow();
        let messageText = new Gtk.EntryBuffer({ text: settings.get_string('message') })
        let messageEntry = new  Gtk.Entry({
          buffer: messageText,
          hexpand: true,
          halign: Gtk.Align.CENTER,
          valign:Gtk.Align.CENTER
        })
        group.add(messageRow);
        messageRow.add_suffix(messageEntry);
        messageRow.activatable_widget = messageEntry;
    }
}

Don’t use an action row, which only expects custom widgets as pre- or suffix to the title label.

You can use the more generic PreferencesRow instead, or consider an alternative UI if the default list pattern doesn’t suit your needs.