- Click the Layers button (or shortcut Y).
- Click the Edit button for the other layer (no shortcut...?).
- Click the X to close the Layers window (or shortcut Y)
- Click the Mic button (shortcut M works in Standalone, but not in the VSTi...?)

An 'E' is displayed in the preset name field when editing the second layer but seems to serve no purpose other than indicating that a 2nd or 3rd layer is being edited. There's no differentiation between those two except that a vertical black line intersects the Q in Pianoteq when editing the 3rd layer which looks like an unintended UI rendering artifact.

As it stands, it's easier to use two instances of Pianoteq in a DAW where I can have both instrument UIs open side by side. But then I have to have two tracks to host them, and this workaround is only feasible for Layering, not Morphing.