For example in frequency LFO what does it mean 0 to 127 values? Absolutely nothing.
A more appropriate unit of measurement would be cents for example or delta-Hz.
This is a feature Yoshimi inherited from ZynAddSubFX. So please submit this feature request at the ZynAddSubFX project. If it's already implemented in ZynAddSubFX, please let me know.
This, like amy other parameters stems from MIDI CC values. Although it would be possible to translate these values, to do this for every single control would be quite a task. For the time being I think we are stuck with it as-is.