How to prevent additions to Chrome search engines (not just default)

There is an extension that prevents additions to the list:

Don't Add Custom Search

Unfortunately, Chrome doesn't appear to offer a built-in way to disable this.

"You can't disable this feature. Google wanted to make things simple so that users don't have to manually add search engines. Power users might not like this feature, but there's no way to disable it."

Source: Google Chrome Help Forum : How do I disable automatic add of new search engines?