How can I tell Visual Studio to format like that? Am I missing any obvious option that my eyes insist to skip?
As of Visual Studio 2022, this isn't possible.
There is an issue on the Roslyn repo that is asking for the same thing, linked to a VS Developer Community post.
Unfortunately, neither of the two have gotten attention, so it hasn't been implemented. You can only adjust spaces around binary operators.
The C# editorconfig reference won't help either: it only specifies a rule to wrap binary operators around spaces, nothing about unary operators.
Your best bet might be to like the related issues and ask for news about them, so they get more attention.
Is there any Plugin out there to do this?
I couldn't find any existing plugins that let you do this, but you can for sure make your own!
There are a variety of plugins on the VS Marketplace that deal with code formatting, like CSharpier for example. You can always fork those to use them as a starting point, and change them so they add spaces around unary operators.
However, it's never gonna be as easy to use as if it was implemented natively.
The closest you can get would be to make your plugin use a different keyboard shortcut as the original code formatting one, have it call the regular document formatting feature and then add spaces around unary operators.
But considering you asked "Is there any Plugin out there to do this?" (implying existing ones), I assume that making your own is out of scope. If you do want to make your own though, check out Start developing extensions in Visual Studio. And if you get stuck, you can always open a new question.