Use the Keyer-YUV to extract a key by adjusting tolerance and softness using luma (Y) and video component (U,V) ranges.
To access the Keyer YUV menu, use:
Batch, then select a node from the Node bin.
Timeline, then use Batch FX (see Creating Batch FX).
The Modular Keyer, then select a node from the Node bin.
This node accepts a front clip and outputs a result.