Routine an aux mix to the main L/R mix

I want to send selected channels to an Aux mix, apply an FX to that mix, then send the affected mix’s output to the Main L/R mix. The Routing and I/O Patch screens don’t let me do this. Only way I can come up with is sending the mix to an output port, cabling that back to an input port, sending the port to a channel, and the channel goes to the Main mix. There must be a way and I would very much appreciate the explanation being for a newbie. Thanks! P.S. I haven’t bought the SQ6 yet but I’m using the MixPad offline to experiment with different setups.

Use a matrix mix to drive the main output, one input to the matrix will be the
main LR mix the other will be the aux mix.

I assume the channels in the aux mix are not in the main LR mix.

Unfortunately the 3 Matrices are already used for something else.

Oops, just realize I can use FX Send 1-4 to get the job done. (Told you I was a newbie!)