From the release note 37416, you can add a username/password combo to the credential library

DataMiner Cube Feature Release 10.3.11 | DataMiner Docs

My question is, where can I use this credentials set and how?

Can I use this during element creation, like the snmpv3 credentials?
Can I use it on a element for filling in username and password parameters based on that credential?

Can I use it in a custom GQI source to store the e.g database credentials of the database I'm querying in that custom GQI source?