Hii wondering if this is possible. Can I have a value default in a dependent pick list based on the controlling field selection (I only have 1 value in the dependent field). So can this be defaulted somehow? Thanks in advance!
Go to the respective object page layout and make the dependent picklist field as mandatory and save page layout.
Lightning Navigation: Setup --> Object manager --> Object --> Page layouts.
While creating a record, select controlling field value then dependent field value will be auto updated. Refer the below screenshot.
Note: Lightning, it works for new records.