I want to add a wet signal from the AUX-channels (a delay on aux1 & reverb on aux3) on my Mackie's subgroup output while recording it individually. Is it possible to do this in some way??
Because i'll only get a dry signal now and can't figure out how to fix it (...without reconnecting some fx boxes in one chain to this particular Sub Out )

if there's not a button to patch your aux returns to a sub, you could return the effects to a channel and assign that whereever you want

I’m a real fool on this.... but do you mean using individual outputs instead of a bus? :-/

no, youd use the SENDS, and then bring the outputs of your FX to channels on the mixer, and then bus those "returns" to the group

OR you sould do the same, and just solo the channels that are the returns

OR...maybe the mixer allows you to solo the returns themselves?

my guess is that thinking about it for a bit will get you where you want to be