I assume I'm doing something wrong or not understanding (not surprising :^). Did a lot of searching but couldn't find an answer.
When using the new "Add Track" dialog, the option "instrument track per output" is always grayed out. If I use the old dialog (by just double-clicking the instrument in the Browser, adding via the Synth Rack, etc.) the option is available. Tried it with TTS-1, BBC Orchestra, Musio, EZ Drummer, etc.
Example with TTS-1:
Use + button to open Add Track dial