To connect attributes using connection lines
icon on the top right hand corner of each node to expand it to its full mode.
Alternatively, you can middle-mouse or left-mouse drag to create connection lines between your output and input attributes.
You can easily find a specific attribute using the search (filter) field. The filter field is hidden by default in custom mode (mode 4). Click
to display it.
To release a connection line, left click on any empty area of the graph, or press Esc.
If you mouse over a compound attribute, the Node Editor automatically expands to expose its children to which you can make a connection.
As you mouse over the available inputs, all inputs that can receive the connection are highlighted. This indicates that it is possible to make a connection with this input.
All inputs that cannot receive a connection are greyed out. This indicates that a connection is not possible.
In addition, it also snaps to the ports to which you can make a connection. This allows you to easily identify the attributes that you can connect to.

To connect attributes without expanding the nodes
