How can I change ITINERARIES vs ITINERARY, which to me is the correct title?
Response: Yes, you can definitely change the string as per your requirement. For this, you need to modify the template file using child theme. Also, you can refer to below-given link to know how you can override the template file using a child theme.
The template file “itineraries-list.php” that you need to modify is inside the path wp-travel > templates of the parent plugin file.
Any chance I can embed another map via iframe
Response: As for now, it not possible as we have not allowed the i-frame in the fields due to the security reasons.
Is there a list of all CSS selectors used within the plugin
Response: As for now, we do not have the list of CSS selector so we are unable to provide you with this.
On the last day, how can I make sure there is a closing dot on the timeline?
Response: To add the dot will require higher level of CSS so as for now you can remove the last vertical line so that the line appears to be finished. For this please add below-given CSS by going to Admin Panel > Appearance > Customize > Additional CSS.