There are 2 Modes, and the feature differ in which mode you are on. You can switch between modes by pressing 'R' on the keyboard.
o- ACTION MODE is the default mode, you can see if it is set to ACTION MODE by the background color. For ACTION MODE it is set to WHITE.
o- ACTION MODE is to move the items around the workspace.
o- ATTACH MODE is to attach inputs and output to the Gate.
o- To highlight a Gate, an Input or an Output, hover over it, red bar will appear at the top. Hovered Gates will show information about the gate on the status bar above the canvas.
o- To select an item,hover over it and click on the red bar, it will turn yellow.
o- To drop an item when selected, just click again.
o- To toggle/change Input values, click on the WHITE area of the Input
o- To attach an Output or an Input to a Gate, click on the Output or Input, it will turn orange, then hover over target Gate possible attach option will appear, click one of them and the link will be created.
o- To re-attach an item that is already attached, attach it to a new target, link will change.