Ubuntu 17.10 windows' menu in panel

You may try a GNOME shell extension called "Gnome Global Application Menu(HUD for Gnome)". It provides a global application menu (i.e. menu bar of an application window in the top bar) à la Unity's global menu.

(screenshot source: extension's homepage at extensions.gnome.org)

For detailed info you may visit the extension's GitHub page.

Warning: Performance may not be as smooth as Unity's global menu. See this if you want to deactivate/uninstall the extension correctly.

Current status and future of the extension

It will work for the next 6 month at less, as i'm waiting for the release of ubuntu 18.04 to take a desition of what i will do. If the default session of ubuntu 18.04 will be xorg i will continue with the extension for 6 month more. Also, if ubuntu or gnome developers fix or help to fix unity-gtk-module in wayland i will continue the extension. What i will not do is continues making improvements, because this have not sense if will not work on Wayland. Also if the ubuntu developers want to implemented it i will donate the extension to hims and i will help in what is needed. - the developer, 27 Oct 2017

Update: The extension has been discontinued by its original developer. Please consider not using this extension.

Ubuntu is now using GNOME as a primary desktop and they are following the GNOME Human Interface Guidelines (HIG). In GNOME they now consider the menubar an inferior solution:

Menu bars increase the vertical footprint of an application’s user interface, introduce a large number of disclosure points, and function as a fixed set of inflexible options. For these reasons, header bars and header bar menus are generally recommended over menu bars, along with other design patterns for exposing controls on demand, such as selection mode, action bars, and popovers.

A global menu is a menubar exported in a service (a DBUS service). So, to have a global menu, as you are wishing, you need to have a menubar or an internal representation of it at least. But most of the GNOME core applications don't have a menubar right now. The Ubuntu developers were working on including a menubar into the GNOME core applications some years ago, but they abandoned that project at the same time they abandoned Unity:

I'm closing the remaining tasks here. The decision was made for Ubuntu 18.04 LTS that we're not going to use distro patches to add these menus back.

While this Ubuntu project existed, a GNOME shell extension called "Gnome Global Application Menu(HUD for Gnome)" was created. But when the Ubuntu developers decided to not support the project, the extension stopped making sense.

So, it is not possible to have a global menu in Ubuntu with GNOME anymore, unless the project of the Ubuntu developers comes to life again, or we find a way to hack the GNOME core applications, or the GNOME designers and developers change their mind about this feature in the future.

Of course we can select an alternative desktop environment in Ubuntu where the core applications have a menubar and then the desktop can implement a global menu for it. This can be for example KDE, Mate and others, but currently not GNOME.

Not having a menubar is a human decision, not an impossibility of the GNOME desktop or the GNOME applications. But the end result is that you cannot have a global menu in a consistent way in GNOME.