Hi there,
another purist solution from my side, as I never clicked with these mega-fiddly “Widget” nodes (KNIME definitely deserves a 
for the most complicated and stressful “Close” button I’ve ever seen!).
What I usually do when a workflow requires direct interaction: Put a Java Snippet node which opens a javax.swing.JOptionPane:
out_password = JOptionPane.showInputDialog(null, "Enter password");
Execute the node, the dialog will pop up, enter the data, and execution will continue.
When you use a Java Edit Variable node, make sure to check Run only on execution on the options.
Hope this helps!
–Philipp