spectrum plot

The harmonics displayed on the spectrum plot can display their peak value when the cursor is moved to the middle frequency of each harmonic.
This does not provide adequate resolution for the thinner peaks, and the left and right arrow keys do not provide a vernier of steps in single increments as seen in other apps.
Is there a fine tuning control available?

Also, is there an option for changing the vertical scale from dB to linear numbers based on 1.0 instead of zero dB?

For advanced graphing capabilities you can export the spectrum data from Plot Spectrum and import it into a spreadsheet, MatLab, specialist graph drawing application or similar.