Service direct link

This option is available If you have the "Change order" option enabled  from "Settings > Booking rules" like this:

You can use that URL to create buttons that link to the front-end booking form with the service is already selected and the category accordion open.

Skip services selection step

If you want to skip the services' selection step when user click on the "Service direct link" just add this parameter:

&skip_service_selection

at the end of the URL