When I click on the lower right hand corner of a list, it condenses it. But how do I un-condense it to view more at once?
There's nothing on the site that lets you condense lists. I'm not sure how or why that's happening. Did you click the 'Add card' text at the bottom of the list? That may have shifted the cards up. If so, just click the 'x' or click off the text input to clear the selection and expand the card list.
If you want more cards on the screen, you can zoom out in the browser.
(That may differ per browser.)