In the Ubuntu 16.04, I very appreciated resizing windows by Ctrl+Alt+Num shortcuts; e.g. Ctrl+Alt+7 resized a window into the top left quarter of the current screen. In the Ubuntu 18.04, only Ctrl+Alt+5 and Ctrl+Alt+0 works. I see a possibility to 'Add Custom Shortcut'. What commands should I use for the other Ctrl+Alt+Num shortcuts according to the Ubuntu 16.04? Thanks!
You can achieve this in Ubuntu 18.04 using the GNOME extension Put Windows.
Version 16.04 uses the Unity desktop and works in a different way.
If you are uncertain as to how to install GNOME extensions you can refer to this easy to follow guide
When in use, left Win + 7,9,5,1,3 keys on the number pad will move the window to top left, top right, center, bottom left, bottom right respectively.