The option to hide preview field titles can be found in different places depending on which extension you are working with. With this setting you can switch between these two ways of displaying preview fields in your list view:
Portal/Shared View
To disable preview field titles in your list view, go to:
Your portal's or shared view's Tables section
Click on the table you'd like to adjust
Layout section
Ensure the Layout Type is set to List
Disable Preview field titles
Form
To disable preview field titles for a linked record field on your form, go to:
Your form's Fields section
Click on the linked record field you'd like to adjust
Layout section
Ensure the Layout Type is set to List
Disable Preview field titles
Note: more settings are visible on this screen if you have added a child form to your linked record field