That’s a great link, Barry!
To add a ToneTwEQ to the Morc, I would replace the A100K VOL pot with a 100K trimmer. You can easily bend the trimmer legs to fit into the Vol pads on the Morc board. Now you will have an adjustable level control to feed the ToneTwEQ. Set it to a reasonable level about mid way. Route the OUT pad of the Morc to the IN pad of the ToneTwEQ. The OUT of the ToneTwEQ becomes the output of the combo.The ToneTwEQ board is so small, it easily fits vertically along a side of your enclosure. The VOL pot of the ToneTwEQ now becomes the Master volume for the combo.