The new settings that are in the instruction, that need to be added to the settings.json file, are shown as "unknown settings" in vscode:

Version: 1.42.0-insider
Commit: cbeff45f80213db0ddda2183170281ed97ed3b12
Date: 2019-12-13T07:05:12.353Z
Electron: 6.1.5
Chrome: 76.0.3809.146
Node.js: 12.4.0
V8: 7.6.303.31-electron.0
OS: Darwin x64 19.2.0
The setting still works, but we should make this visible now that the extension has been announced in preview.
Yeah, I can do that. Will add one for EH debugging too.
Still showing as unavailable with the latest release.
It will be in the next insiders on Monday
After updating to the latest Insiders, "debug.node.useV3", along with one for "extensionHost" are now showing as available, but the debug.chrome.V3 is still not enabled:

I haven't republished the extension yet.
Several versions of the extension have been put out, and the debug.chrome.useV3 still shows as an unknown setting.
Name: JavaScript Debugger (Nightly)
Id: ms-vscode.js-debug-nightly
Description: An extension for debugging Node.js programs and Chrome.
Version: 2020.1.5284
Publisher: Microsoft
VS Marketplace Link: https://marketplace.visualstudio.com/items?itemName=ms-vscode.js-debug-nightly
This setting is still showing as unavailable, as of the latest Insiders version and latest version of the extension:
Name: JavaScript Debugger (Nightly)
Id: ms-vscode.js-debug-nightly
Description: An extension for debugging Node.js programs and Chrome.
Version: 2020.1.31743
Publisher: Microsoft
VS Marketplace Link: https://marketplace.visualstudio.com/items?itemName=ms-vscode.js-debug-nightly
Version: 1.42.0-insider
Commit: c4d53a19df8799f5d49a4f49a6900c499e6fa27c
Date: 2020-01-23T05:38:55.065Z
Electron: 7.1.7
Chrome: 78.0.3904.130
Node.js: 12.8.1
V8: 7.8.279.23-electron.0
OS: Darwin x64 19.2.0

Most helpful comment
Several versions of the extension have been put out, and the debug.chrome.useV3 still shows as an unknown setting.
Name: JavaScript Debugger (Nightly)
Id: ms-vscode.js-debug-nightly
Description: An extension for debugging Node.js programs and Chrome.
Version: 2020.1.5284
Publisher: Microsoft
VS Marketplace Link: https://marketplace.visualstudio.com/items?itemName=ms-vscode.js-debug-nightly