I tried today to wrap some nodes into a wrapped meta node. This Meta Node has a Flow Variable input. But these Variables are gone inside the node. I cannot access them using any embedded nodes.
For conveinience I append a workflow creating two Variables and a Meta Node having only a flow variables port. Inside the node you will not be able to see the variables.
By default, flow variables within a wrapped metanode have local scope. If you want to pass them in, you need to configure the WrappedNode Input node inside the wrapped metanode. See screenshot below.