AFAIK it’s currently not possible to assign the same MIDI signal to two plugins.
What you can do, however, is use CV for this.
- add one “Control to CV” plugin to your pedalboard
- assign that plugin’s input to your Boss Pedal
- in the Web UI’s top row, enable “show CV” (might be called slightly different, I’m not near my Dwarf ATM)
(EDIT: It’s called “manage CV ports”) - click on the little box on the output side of the Control to CV plugin, give it a unique name (e.g. “Pedal Control”
- now you can assign the CV “Pedal Control” to as many parameters of plugins as you like (in the plugin’s settings, open the parameter settings and instead of assigning a MIDI, choose “CV” and then select the “Pedal Control”).
See the wiki about CV: CV Tutorial - MOD Wiki for more on this (" Setting up Macro-Controls using CV" is the chapter you are interested in).