To disable text wrapping, the eventTextWrappingEnabled value must be set to false. It adds "whitespace: no-wrap" style to the event element.
See also:
https://api.daypilot.org/daypilot-scheduler-eventtextwrappingenabled/
If it doesn't work, you'll need to review the CSS of your custom theme. I recommend using the browser developer tools to inspect the event element and see what styles are applied.