How to Create this Popup signin page in Bubble?

[Zeroic]

You can do this using custom JS via the Toolbox plugin. This is the code to achieve something like this

// Function to open prompts for username and password
function getUserCredentials() {
    const username = prompt("Enter your username:");
    if (username !== null) {
        const password = prompt("Enter your password:");
        if (password !== null) {
            alert(`Username: ${username}\nPassword: ${password}`);
        } else {
            alert("Password not entered.");
        }
    } else {
        alert("Username not entered.");
    }
}

// Call the function to open the prompts
getUserCredentials();

Let me know if this works