How to add a separator to Gio::Menu - c++

Question

I'm writing an application using GTK3 and gtkmm. I'm adding a menu button to the header bar. So far, I got items to show up, but I can't add a separator.
Here's where I create the menu:
auto main_menu = Gio::Menu::create();
...and add some items:
main_menu->append("Export to WAV", "app.exportToWav");
main_menu->append("About", "app.about");
And here's what I get:
But I want to add a horizontal line between the two items. There seems to be no obvious way to do this with Gio::Menu, and I want that popover. I tried adding an item with "-" as its content, but that did nothing. Gtk::SeparatorMenuItem exists, but it doesn't seem to be compatible. Is this even doable with this kind of menu?

Answer 1

I've figured it out. Turns out, with Gio::Menu, you don't specify "separators," per se. Instead, you specify sections.
Essentially, what this means is creating multiple menus, and then grouping them all together in a single menu using the append_section(Gio::MenuModel) function.
Here's what I ended up doing:
// Create master menu
auto main_menu = Gio::Menu::create();
// Create menu sections
auto main_menu_section1 = Gio::Menu::create();
auto main_menu_section2 = Gio::Menu::create();
// Add item(s) to first section
main_menu_section1->append("Export to WAV", "app.exportToWav");
// Add item(s) to second section
main_menu_section2->append("About", "app.about");
// Append the new sections to the master menu
main_menu->append_section(main_menu_section1);
main_menu->append_section(main_menu_section2);
Then, each section is separated by a horizontal line:
It's faint, but it's there