Can we create our login page and login in runtime SCADA?

I want to switch users in the SCADA system. Wherever double authentication is required, a pop-up should open with username and password fields. When the user clicks the login button, the selected user should log in. Instead of entering the username and password in the Ignition username and password fields, can we create our own login page for user authentication?

Have a look at the linked resources for information about doing double authentication using the authentication challenge.

No, not in Perspective, because the IdP is a separate (possibly third party) mechanism that has its own username and password entry and it's a big no-no, security wise, to hand credentials off like that.