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Ahh, I was missing the last little step of clicking +Add after selecting my primary and foreign keys from the drop down. I mistakenly thought that would add another row of primary and foreign key. At any rate, that did the trick. Thanks so much!
I seem to be unable to designate an existing column name as the foreign key. I only have luck if I drag the reference line and let Vertabelo create the foreign key column name for me. In my case, I want to capture the way we contacted a customer, be it email, Facebook, twitter etc.

For example table A has the following fields:
• CUSTOMERS
• CONTACT_CODE
• CONTACT_DATE

And table B has the fields:
• CONTACT_CODE
• CONTACT_CODE_DESCRIPTION

I don't seem to be having luck simply trying to edit the reference between the two tables making CONTACT_CODE in table B a foreign key to table A. I keep getting a new field named TABLE_A_CONTACT_CODE_ID.