Question: System Settings can be run from the launcher (pinned by default), the Dash, or the power cog. But what command would I enter in a terminal window if I want to run it from there?

Answer: 
For [Ubuntu Mate](https://ubuntu-mate.org/) the command is `mate-control-center`.
Well,
in KDE NEON 5.16.4 (Ubuntu 18.04), it is written in the "System Settings Handbook":

> 
> The System Settings can be started in one of three ways: 
> 
> 
> * By selecting **Settings → System Settings** from the Application Menu.
> * By pressing `Alt`+`F2` or `Alt`+`Space`. This will bring up the KRunner dialog. Type `systemsettings5`, and press `Enter`.
> * Type `systemsettings5 &` at any command prompt. 
>  All three of these methods are equivalent, and produce the same result.
> 
> 
> 

In my case, I needed to configure my HP LaserJet settings. Doing this as user, after applying and saving, they were ignored. So I think I had to do this as root and the settings are stored normaly now, so, each time the user opens the print dialog, the system remembers that I want log side binding and 1200 resolution :=)

I thought that `sudo systemsettings5 &` was enough, but as Zanna suggests: *It should also be recommended to use 'sudo -H' if opening a GUI app with sudo*.