A long time ago this was addressed:
There’s also still an open Github on this over at https://github.com/brave/brave-browser/issues/694
That said, to my understanding there’s no “official portable” version. You can always grab older files like was mentioned by @talgeeze. And then there’s the outdated ones that someone else did at https://github.com/portapps/brave-portable but it seems they haven’t touched it since September.
It’s called Search. So you know where you mention:
You notice on the top right, there’s a search? If you type in Release Notes then it will ONLY show you options for Release, because no other versions have Release Notes. This would put the LATEST version right on top for you.