GtkApplication with different ApplicationWindows

[zahlenmeer gmx de]

Hi everyone,
I am working on a project where I am struggling to decide which
classes/objects I should use. I use gtk3 but it's still a classical
application, so no fancy appmenu, CSD and not primarily designed for the
Gnome DE.

The program works as follows:
- A unique main window, with a main menu bar
- Multiple task windows, all with a task menu bar
- The program can be called with ./prog --task to only open the task
window, not the main window

The first thing one would find in the documentation is GtkApplication
and GtkApplicationWindow, but those have some limitations I currently
don't know how to deal with:
- Different menubars for different windows (main window vs. task window)

So the idea would be to use a normal GtkWindow for the task windows, but
in this case I have:
- Application life-cycle without a GtkApplicationWindow?

So for me the most promising solution would be to skip GtkApplication
and GtkApplicationWindow at all, using plain GtkWindows and writing my
custom application class. Of course this means extra work to get all the
nice benefits GtkApplication offers out of the box.

Do you have any ideas how I could design my application accordingly?

Kind regards