I just started out with Anvil and created a new project based on the classic theme, which uses cards to display content. I am developing mainly for normal web browsers (i.e. no mobile). If the browser tab is not too wide, then these theme cards look fine:
Look for a “full width row” checkbox in the Parameters section on the right. You might have to expand the bottom subsection to see it.
Thanks, that did the trick - or at least half of it. For the records, I also had to set that flag accordingly when I programmatically add the form (i.e. content) to the card: