Apple Shake 4 - Manual (Page 233)

Chapter 7 Using the Node View 233
To connect several nodes to a multi-input node at once:
1 Select all of the nodes you want to connect to the multi-input node.
2 Shift-click the plus sign input of the multi-input node.
All selected nodes are connected.
One Input, Many Outputs
Any single input knot on a node can only be connected to a single noodle. This is true
even for multi-input nodes—each input knot can only be connected to a single
noodle. If the node you want to connect is already attached to another noodle, the
previous connection is broken, and replaced by the noodle you’re dragging.