I agree that this is most likely not the number one complaint as there are more development impeding bugs in the engine far more important than this.
Also, if you think about what you are looking for, a “show/hide” feature, assuming you mean removing windows out of view that you may not use often or at all for that matter. The engine does have a dragable interface, you can reposition panels where you like them best or even move them to a seperate monitor to increase viewport area. As with most digitial editing software, you can also go to “Windows” on the flie toolbar and uncheck things you dont want on your screen. UE4 is very much customizable already.
On a side note, if people are saying they want the engine to look and/or feel more like the Godot engine. They solved their own issue, use Godot instead, it’s apparently exactly what they are looking for.