A few questions/comments based on what limited info is available.
1) Curious as to why the Master/Slave mode? Couldn't this be accomplished by simply normalling the CV jack to the row above? This could potentially enable the same CV to be a toggle one row and be level on the next...for lack of a better term "overloading" the functionality of a single CV source.
2) when master/slave, can one switch be 2 in>1Out and the other 1in>2out etc?
3) reply " or by the state of the manual control button (not pressed = I/O1, pressed = I/O2)"...
would actually prefer manual toggle on/toggle off each press than a "hold on, release for off" for a number of reasons. (space to operate when patched, not losing a free hand, lifetime of the button, personal preference)