This is some great feedback! I will make sure that I pass this up to the DIGITS dev teams. In the meantime, you may want to consider, don't hate me for this, but maybe a 3rd google account that has a combination of both contact lists and use that google account within DIGITS.
Looks like it would be pretty easy to export both your contact lists and import them to the new account using the steps provided by Google Import, restore, or back up contacts - Gmail Help
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