Constraints tab is empty

For some reason the Constraints tab is empty. 16.0.64.1478

For me, it is not blank. Which Oracle version are you using, and do you mean SB-Tables-Constraints, or SB-Constraints?

SB-Tables-Constraints
Oracle 19.6.0.0
Client 21.3 (Could it be because of that?)

Oh, I see it now.
No, it's not because of your client.
Thank you for reporting it.