This article talks about a way to achieve this on Confluence Server and points out it's not possible to use the same solution in Confluence Cloud.

Could another approach be offered for Confluence Cloud? As an admin, right now the pencil icon along the sidebar allows me to hide other things such as the Blog or Overview. It sure would be great if we could do the same for Space Tools.

The use case is that we're considering moving our public docs site to Confluence, but the Space Tools exposes some internal stuff (e.g. names of Administrators) that we're not really keen to open up to the world.