Hi Johannes,
I tried and think Maximo Anywhere apps can work with username/password stored on iOS Settings > Passwords & Accounts > Website & App Passwords .
What I did was, firstly store the username and password at Settings > Passwords & Accounts > Website & App Passwords; then open Work Execution app, at the login page click at username field, the keyboard shows up with "<key icon> Passwords" at the top of it, click on it, AutoFill Password dialog appears, choose the username stored, returning back to the WE login page, click at either username or password field, the username and password are auto filled, logging with that is successfully without any problem.
Not sure if this is what you are after?
Angela, Jinhui Li
Maximo L2 Support (Asset Management)
------------------------------
Angela JINHUI LI
------------------------------