2. Creating Layer Connection
Holding Alt and dragging from one layer to another
You can create a Texture Layer Connection by holding Alt and dragging from the source layer to the destination layer. This will find the first texture variable in the source layer and set it as the source of the first texture variable it finds in the destination layer.
Dragging Texture variable
If you drag a texture variable of a source layer onto the destination layer (Send Texture layer), a Layer Connection is going to get created.
Using Layer Connection Window
You can also create a layer connection manually in the Layer Connection window.