Hello @jakstcr
First of all, thank you so much for using WP Travel plugin.
Regarding your query, first of all, let us make you clear that any changes that you make in the core file of the plugin will revert back once you update the plugin. Therefore, we request you to make the changes in the child theme rather in the main file.
Also, referring the changes to the codes via support forum is out of the scope of the support forum since, in worst case it can cause some fatal issues. We need to know the changes and requirements in detail for precise result. For any kind of assistance further, kindly refer to Hire our Customizer service.
Hoping for your kind co-operation.
Regards!