EN16, master encoder (to control the others)

for i = 1, 16, 1 do
    if self:element_index() ~= i then
        element[i]:encoder_value(self:encoder_value())
        midi_send(0, 176, i, self:encoder_value())
    end
end

What this code snippet will do is iterate over all the elements on the module and add set the encoder value of the encoders to the one where this code is running from and send out the midi as well.

The CC part of midi_send is just going from cc 1-16, this could be more nuanced when exact CCs are needed

With a bit of modification a quick reset can be done with this as well

This question becomes more nuanced, if you want to keep the setting of your encoders AND just relative to those settings increment / decrement them based on a master encoder.

If you can let me know your level of familiarity / experience on coding, I can guide you further.