In a grey info block in the beginning of Section 5.3. Edit Tab" the manual say that "The Edit tab canīt be selected when working in Spectral mode." So that's by design.
You can work with additive synthesis per harmonic in Time Synth/ Edit mode.
In the manual you can read this in section "5.2.3. Spectral Synth Mode":
"In Spectral Synth mode, the spectral display shows a basic evolution overview of the
harmonics which can be edited by using the corresponding parameter in the Evolution
section. Further editing in the graphic display is only possible on the Edit page [p.32]."
One get the understanding, that one somehow can work/ edit futher on this per harmonic. But unfortunately it's not possible. So either the manual is incorrect or there is a bug. As the EDIT tab is'nt availble in Spectral mode, then i assume, that the manual is incorrect or unclear, but i can't tell for sure.
It would be nice to be able to do some additive editing in Spectral mode, and then work further on that per harmonic just like the manual somehow give the impression you can, even if it perhaps not will be possible to do it the other way around. It look like this have been the intention but perhaps not possible. Or the manual is incorrect or very unclear.
As it is, then it's only possible to select a waveform both in Spectral mode and in Time Synth mode, and then work further on that per harmonic in Time Synth mode. That's done by setting levels per harmonic using an envelope setting for each harmonic. It's quite flexible and can give a complex dynamic changing waveform.
You can convert samples to synthesis and then work further on that in Tome synth mode.
