UDMF Controls plugin lets you edit surface properties and linedef/sector UDMF flags quickly.
Default key: Ctrl-T.
Found in: Preferences -> Controls -> Tools -> Open UDMF Controls.
Usage: select some surfaces in Visual Modes, then open UDMF Controls panel to edit surface properties and linedef/sector UDMF flags. If no surfaces are selected, currently hilighted surface will be used.
When Relative mode is active, scale, position and rotation are changed relatively to their initial values.
You can press Shift, then click inside Rotation control's dial to snap angle to 45-degrees increment.