Please make it possible to grab a block, drag it onto a existing connection between 2 other blocks then release it to insert it between.
The connection might light up if the block the mouse cursor with the block is at the right position for insert.
For more wonderful node handling please look into NUKE, The Foundry have found many very practical ways for handling nodes very efficiently.
Things like extract blocks without severing the connection between the predecessors and following nodes.
Or grabbing connector-lines at the ends and reconnect them in other ports.
Selecting and moving the actual node and all following by holding CTRL when clicking.