Shifting Spectra Interactively

In a 1D SpectrumDisplay it is possible to move and scale the spectra interactively relative to one another. When you right-click on a Spectrum in the Spectrum toolbar you can select to make the spectrum Current. The spectrum button in the toolbar will now have a narrow blue outline to indicate that it is active. You can make as many spectra current (or active) as you like. While holding down the Option key you can now use the arrow keys to move the current/active spectra left/right/up/down and the middle-mouse wheel to scale the active spectra relative to any other non-current/active spectra in your displays.