Searching for a theme compatible with a particular booking engine or vice versa searching for a booking engine which is compatible with a particular theme is very, difficult, time-consuming and ends up wasting a lot of time for everyone as you either need to buy the theme and often end up requesting a refund or spend hours trawling through often inconclusive documentation.
Could Envato please add the booking engine underlying each theme to the compatibility list where bookings, appointments or calendars are involved.