From your suggestion I tried to add the line just like you show. I even looked a ST documentation and they seem use in the same manner. However when I add it to a Hubitat Driver I get a "No signature of method". Darn I just realized I didn't specify the text I'm trying to add is in a driver. Perhaps that makes a difference.
You should not have to hit configure after saving preferences. You can automatically do that by adding a call to your configure() method from your updated() method. The only time the user should have to press configure is after swapping drivers.
Your type should be what type of input you want to have, i.e. "number", "string", "enum", "bool", etc. What you are missing is Title. Title and Description would be your two available text fields in an input. I do not believe Element is a supported field for a in input.
I should add: If this were functioning code I would be very concerned about type etc. However since this is displaying dumb text I'm willing to "bend" the structure.