Hi @CLSecrest,
Do you mean that you popualte the Dropdown box with data from a collection, once you go to edit mode, nothing populated within the Dropdown box, right?
Actually, it is a normal issue when you refer to different data source in a Form.
You need to retrieve the data from the data source that you used to populate the Form.
For example, I populate the Dropdown box with a field from the collection by setting Items propetry to:
Col.FieldName
Then you need to set the Default property to:
LookUp(col,Field=ThisItem.Field_In_List).Field