Disk Utility not showing "free space" on external drive
I've got a 4 TB Seagate Drive that I originally partitioned into 1 TB and 3 TB using Mac OS Extended (Journaled). Since then, I decided to reformat the 3 TB partition, and I changed it to APFS format with two volumes and deleted the 1 TB partition. My plan was to merge the 1 TB into the 3 TB partition.
When I mount the drive, Disk Utility only shows the total capacity of the drive as 3 TB:
For some reason, the 1 TB of free space from the deleted partition does not appear in Disk Utility. It also does not have a disk identifier in Terminal:
How do I recover / reclaim / allocate the 1 TB of "free space"? Thanks.