When testing API Endpoints of applications running on BTP, it can be necessary to authenticate using the right S-User credentials. In such a scenario, the Universal ID password will not help.
Universal ID password can be changed via https://accounts.sap.com (will forward to the Standard SAP ID Service)
A specific S-User password can be changed via https://account.sap.com (will forward to Manage my Account, where you see the different S-User and P-User, linked to your Universal ID)