Tongue
If you are not familiar with creating shapes yourself, the Unified Expressions documentation on VRCFaceTracking can be a good reference.
The tongue has several modes of operation. Choose one of them:
Mode: Independent
If you choose Independent mode:
Forward
Pull the tongue so that it crosses the lips. Use the purple handle to increase the radius of the pull.
You can click on the Jaw Open shape to test how the tongue will look when the mouth is open.
Up/Down/LeftRight
Press "Reset position and rotation". This will put the gizmo at the same location as Forward.
Move and rotate the gizmo so that the tongue matches the corresponding shape.
The tongue setup is particularly finnicky and is likely to be changed during the course of the early access trials.
Mode: Pull and Direction
This mode is not currently available.
If you choose Pull and Direction mode:
Forward
Pull the tongue so that it crosses the lips. Use the purple handle to increase the radius of the pull.
You can click on the Jaw Open shape to test how the tongue will look when the mouth is open.
Up/Down/LeftRight
Press "Reset position and rotation". This will put the gizmo at the same location as Forward.
The gizmo will act just like a "Pulling and twisting" shape, based on the tongue being pulled forward.