Using a reference should be the answer. What was your problem with them?
Right click the terminal and select Create>>Reference, then right click the reference and select Create>>Control. Copy this control (the reference) to the subVI and have it as part of the connector pane. On the BD, wire its terminal into a property node. Since you created it from a specific control, it should give you all the properties of that control. Place the subVI on your BD and wire the reference from the original control into it and it should work. If it doesn't, I suggest you post the code.
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