Rider Swap (RS)
Rider Swap Genie+, ILL, and Virtual Queue can be used with Rider Swap (which is also available for Standby riders - continue reading below). To skip the Standby line, all riders must have a LL reservation (or Boarding Group, if applicable). Non-riders (i.e., children under the height requirement) do not need a LL reservation.
After reporting to the LL, a CM will scan all LL reservations and assign a RS pass to Group 2 riders (1 adult waiting with non-riding child(ren) plus one repeat rider). Group 1 riders will enter the L immediately. Group 2 will return to the LL after Group 1 rides. One rider is able to ride twice (once in the first group, once with the waiting adult). The RS pass does not need to be redeemed immediately, but each guest can only have one RS pass at a time (two adults and respective repeat riders in a party CAN have a RS pass for separate attractions but the RS holders may not overlap).
Using Rider Swap without a LL reservation / Boarding Group works the same way, except Group 1 must wait in the Standby line rather than using the LL. Group 2 returns to the LL entrance. No one needs a LL reservation or BG if Group 1 intends to wait Standby. Instead, everyone gets in the Standby line and at a certain point, a CM will assign a RS pass to the Group 2 riders, at which point Group 2 and any non-riders may exit the queue. In many cases, you can send runners up to the CM checkpoint to get MagicBands / admission scanned while the rest of the party waits in line to save time.