You can hide layers in the Scene view by clicking on the ‘Layers’ dropdown in the top right of the Unity Editor. By clicking on the eyes in the dropdown, you are able to toggle elements on and off in the scene view. There is also a shortcut for ‘Nothing’ and ‘Everything’.

Here is an example of the ‘UI’ layer being hidden in the scene view…

And here is the exact same scene with the ‘UI’ layer showing…

This is particularly helpful for isolating UI canvases in some scenes or keeping them out of the way whilst you’re working on the environment. It is also helpful for isolating sections of the environment and keeping the scene view uncluttered.