On this occasion, I would like to share a tutorial regarding how to make a new window in Ubuntu in the middle of the screen by default when it's first opened. For the tutorial itself, in this video there are 2 ways, the first is through the terminal and the second is through tweaks. Here is a description of the steps:
Via Terminals:
1. Open the Terminal application,
2. Type the command "gsettings set org.gnome.mutter center-new-windows true",
3. Press Enter,
4. Done.
If you want to disable this command, you can simply type the command "gsettings set org.gnome.mutter center-new-windows false" in the terminal.
Via Tweaks:
1. Open the Tweaks application via the Show Applications menu,
2. Select the Windows menu,
3. Activate the "Center New Windows" feature/button,
4. Done.
Hope it is useful.