Debug Assistance - pinpoint error

Currently we have an issue testing a workflow where it gives us "Semantic Errors" when we try test the workflow. When we try to publish the workflow we get the following "Some fields contain references to invalid variables; we recommend removing these invalid references. When you publish the workflow, all references to invalid variables will be removed." So clearly there is some kind of check happening, but it would be great if it would tell us which action has the problem, and which variable. We have over 600 variables, and hundreds of actions. So trying to find this is like trying to find a needle in a haystack. It would be good if there was a debugging option that actually showed you where the offending issue was.