On Windows 10, the Credential Manager displays it as follows:

Logitech uses / for separation:

Microsoft adds some key-value stuff, but I like the Logitech one better --> is it possible to replace the | with a /?

No, the pipe char is hardcoded in the java-keyring library.

https://github.com/javakeyring/java-keyring/blob/77358e960584109127835194320ca6061e9eac6f/java-keyring/src/main/java/com/github/javakeyring/internal/windows/WinCredentialStoreBackend.java#L59

Some implementation changes were discussed:
The API keys should always be stored in the keyring an not in the preferences anymore at all.
The proxy config should directly include the option to persist the password instead of an abstract general option to use the key store.

Was this tested and confirmed using Ubuntu / GNOME? It doesn't work as Keyring.create() repeatedly returns null. I'd say this is OS specific, but do we understand where and when it won't work? When not possible, password saving probably shouldn't be provided as an option (as it's misleading behaviour). Current behaviour is to swallow exceptions, etc...