If I moved the fourth mixer track over two spaces, it would change the output of the FPC in the channel settings window to 3, and my drums would sound the same. If I put a whole bunch of effects and stuff on mixer track #3, and then moved the fourth track one space to the left, the third mixer track would become the fourth, but the pad in FPC would still be sent to the third, and then I’d get mad because my drums sound bad all of a sudden. If I open up FPC’s channel settings window and send it to mixer track #2, and then set the output offset of a pad to 1, the output of that pad will be sent to mixer track #3.
FPC’s multi-outs work by offsetting each pad’s output from the mixer track that FPC is sent to, in the channel settings window.
The mixer tracks that individual instrument channels are sent to will change if you move stuff around, buuut multi-output plugins (or at least FPC) will not change which tracks the multiple outputs are sent to. Using this to re-arrange stuff could make some things easier, but it could also screw everything up and be frustrating. Pressing Alt+left arrow or right arrow with a mixer track selected will move it around. Finding these things is a great joy to me.
There are a lot of features and functions in FL Studio that aren’t immediately obvious and aren’t mentioned that much, but are very useful.