I don't think there's a viable way to do this. While you can programmatically collapse a category in a PropertyGrid
control, you'd need to get access to the instance being used by Visual Studio (or whatever editor they're using). As far as I know there's no way to control that declaratively, e.g. with an attribute or anything.
It might be possible with a custom UITypeEditor
or something, but it would be fragile and need an awful lot of effort, and personally this feels like the kind of thing that should be left to the users' preferences anyway.