A common pain point is when you create a sub-graph inside of a graph that has a very large number of inputs and you have to one by one click on all the drop downs for each of the inputs in order to 'pass-through' inputs from the parent to the child. A good feature request would be to in some way 'match' the name of the graph input on the child to the ones that already exist on the parent and try to 'auto-complete' the inputs.
One easy way to do this would be to simply put exact matches on graph input names at the top of the drop down list when will in the inputs from the parent.