Slightly baffled by this: Scrivener DOES have a "main central big editor window" as a default feature...

But you can set up Scrivener workspaces to do anything you like. In some of my files, I have four windows open simultaneously. In others, I go for two, side by side. Sometimes I just use that big ole' main central editor window. You can save out multiple workspace configurations and reload them whenever you feel like a change of focus.

The biggest difference though is in the main central big editor window. This is
where it gives Scrivener a run for it’s money and what Scrivener should have as a
default feature.