I have seen a few pictures of dual extruders both running at the same time, but how is it done?
I do not think it can be selected like that in slic3r. I thought about making a Y-cable for the stepper motor as one possibility.
The main reason I want to do it is to easily calibrate the exact extruder offset in X and Y, but there are other high production possibilities.
Any ideas? maybe a certain G-code, or a find and replace in the G-code?