The 3d viewport has needed this for a long time now.
In the editor, I can’t even count the times that I have inadvertently moved an object, static mesh, brush, etc. I can’t be the only person who has done this or who does this often. Especially when you have a map filled with stuff.
In modelling applications like 3ds max and blender, there is a ‘selection’ mode, where you can’t move or manipulate anything. Why is there no such mode in the editor?
Here are some screens for context:
and
And please, don’t be one of these 
And say some dumb garbage like “oh just use the world outliner”.
Everyone has their own workflow, and I can’t be the only person missing this functionality.