Create new row action with date field values from other models

I’ve got a ow action on table with a Patients model that Creates a New Row on my Cases model and sets some field values. I’d like to set values for some date fields on the new row based on values in the selected Patient row, like {{Date_of_Birth__c}} but I can’t type that in, only select a relative date or a specific value. 

Can I get around this in the XML?