Using Harrison plugin this feature works great and I use it to create stereo field using 3D Delay by bypassing one channel and removing instances and adding to the right only. Is there a plan to include these feature on 3rd party plugins? 3rd party plugins don't have the option to add or remove instances in pin connection.
I believe you can add instances of 3rd-party VSTs on Windows, but not AudioUnits on Mac. Because AudioUnits already have their own complicated rules for adding and subtracting connections.
This is why ( for example ) VST's and LV2's often come in mono and stereo versions, whereas there's only one version of an AU plugin: the host is supposed to ask the plugin what format(s) it supports, and then configure it on-the-fly. This is a cool design, but it is hard to mix&match with the more traditional plugin designs which act more like hardware... with a fixed set of Input and Output pins.
-Ben
Audio Units have a button "Add/Remove Input Ports" instead (the instances are implicit).
VST, LADSPA and LV2 (which have a fixed port count) have an "add/remove instance" option.