How to output custom fields?

I am using the plugin to generate a list of refurbished bikes which are available to people in our community who are on low incomes. I want to make it easy for people to see which bikes are the right size for them. I have some custom fields linked which hold that information. So in the Post Appearance, rather than selecting Title, I would like to display ‘Bike Number’, ‘Make and Model’ and ‘Frame Size’.

I guess it is beyond the scope of the plugin to be able to pick custom fields visually, but I wondered if it is possible to write something in the short-code to display custom fields? Or if not, are there any hooks within the plugin which I could use to write a filter for my own output?

Thanks again for such a flexible and useful plugin.