The main board handles my Presets and Scenes layouts.
The three pedals on the main board are Pedal 1-3 in the FM9.
The 8 switches in front on the main board are switches 1-8 on an ExpressionIO under the board, and mostly trigger momentary effects changes.
The sidecar board handles per-preset effects and/or effects channels, though a number of switches have become cemented into the layout, particularly in View 2, where I hide switches for choosing channels on a number of effects.
The buttons in front of the sidecar board are a switch connected to FC1 Pedal 1, and 'utility' functions: preset up/down, scene up/down with FC Layout switch and View switch on hold.
Main board:
Sidecar board: