the best way to make this is select in the Masterlist/competition startlist the rider you want to add in the new list/competition ( example for GP qualification ) by checking the box on the front of the rider/horse line and when all riders are selected, copy to the new class.
The only thing to know is all the data will be copied into the new class ( Results, starting order , ... that have an incident on the accounting part) so when you are in the new competition/list where you've copied riders and you want to delete datas, go to "Edit" then select "All" then "Edit" then "Clear" and hold the "clear all results" to delete the results data in the now list/competition.
Laurent :)