Scene tree (left), Viewport (center), Inspector (right), FileSystem (bottom).

F1 = 2D, F2 = 3D, F3 = Script. Or click tabs at top.

Hide all panels for clean viewport. Press again to restore.

Toggle Output, Debugger, Audio, Animation panels.

New grayscale 'Modern' theme is now default. Cleaner, more focused look. Switch in Editor Settings → Interface → Theme.

Bottom panels are now regular docks. Drag them to any side or float as windows.

Click the tab menu button to see all open scenes/scripts. Hover-switch tabs while dragging.