With 18.3 and 18.4 at least, when I right-click on the connection that uses Wallet, it asks for my username and password. I shouldn't need to enter username/password when using wallet. When I right-click, properties, then click connect or test, it works without asking. I'm on Windows 10 and Oracle 12.2, Instant Client 18.3, but it also happens on Windows Server 2008 and Oracle 12.1, Instant Client 18.3
This didn't happen with older SQL Dev versions I don't think.