The 2020.01 release saw the introduction of Per-Output Instrument Tracks, which allows you to create multiple Simple Instrument Tracks routed to a single instance of a VSTi. In order to use this feature however, you must map the MIDI channels within your VSTi to the relevant output. This must be done inside the VSTi itself, and each VSTi handles this differently. For example, to do this in TTS-1: