I found out how to do it in Firefox and Google Chrome.
Maybe someone else out there knows how?

@burnout426 Thanks, but that's not what I asked for. I am already using some of those switches.

What I need is the ability to configure Opera from a batch file, either before, during or immediately after installation, to set the following, among others:
Set "show bookmark bar" ON
Set "block ads" ON
Set Block trackers" ON
Set VPN ON
Set "Ask where to save each download" ON

In addition, I want to preinstall some add-ons, including:
"I don't care about cookies"
"Google translate"

These all need to be set when Opera is installed, before it is launched for the first time, so they will be the default settings and add-ons for every new user.

I wrote a batch file to automatically install and configure the standard apps on a new build. I can install Opera with a Chocolatey command, but I would also like to pre-configure certain settings which every new user would get. I found a very old (ca. 2001) post about using an opera.ini file, but the current version does not appear to have this file, and the documentation that I found makes no mention of many of the settings that can now be made from the GUI.