How do I move the window menu to the window title bar in Ubuntu 18.04?
You can do that using (GNOME) Tweaks (previously known as (GNOME) Tweak Tool). First install it if it's not installed by running
sudo apt install gnome-tweaks
(or sudo apt install gnome-tweak-tool
).
Then launch Tweaks, go to "Top Bar" section and toggle off the "Application Menu" option.