2 issues:
1) The manual section 4.1.13 'Reverberation' refers to 6 items - and the image 'The reverb module' shows only 2 of them.
The other items are 'Mixer' items, but this is not mentioned in the section heading.
2) There is a jack with no label at all. It's not explained in '4.1.13', even though it *is* in the manual image 'The reverb module'.
It's the reverb output.
Perhaps 'reverb out' could be a) added to the manual, and b) labelled on the front panel.
Cheers Jeff