I’ve experienced a strange behavior of workflow credentials configuration dialog.
I created an empty new Workflow. First I hecked workflow.knime file I can see an empty XML element for Workflow Credentials ready.
Now I open Credentials Configuration dialog from a local menu of my workflow in Knime explorer view.
I fill a credential name, login and password.

I confirm the dialog and the Workflow Credentials Configuration dialog

I can see credentials (name and login, not the password) saved in the workflow.knime file after I save my workflow.
Now I open the Workflow Credentials dialog again:

And I see no credentials anymore!
But if I try to re-create my credentials:

KNIME recalls somehow it actually knows about the credentials:

Not even after I click the OK button I can see my credentials.

The only way how to get my credentials visible is to add another one:

And WOW! Here we go:

Lets close it by clicking OK and open again:

It shows just the last credentials added.
I close the dialog, save the workflow and open the dialog again:

…exactly the same as above.
Well, let’s add another one:

…press OK and you can see:

A miracle.
Close and reopen:

Just two last credentials. I suppose the dialog hides the first credentials configured. Zero / one based array indexing problem? May be.
Now let’s close the dialog, then save and reopen the workflow. It opens credentials configuration dialog while the workflow is opening. No surprise. The first entry’s missing again:

But we still have everything in workflow.knime file: