Hi,
You should be able to get close to what you're looking for if you set the MIDI mode to "Routed." This mode will sustain the chord you've played until you play a new chord.
It sounds like what you're looking for is "Gated" mode, but with the ability to sustain the notes with an external pedal. This isn't currently possible, but I've brought this up as a feature request that may be added to a future version of the plug-in.
