How consolidate Multiple Process Instances in only instance

HI guys, imagine i have 4 instance of process, and need consolidate all instance in only one instance,
how i can does?

An example: i have 4 Purchase requisitions and need consolidate in 1 purchase requisitions for finish request
Thanks!

@Facundo_Rodriguez_La if you would like to handle all the 4 purchase requisition in one process instance then you can go for “Multi-instance sub process

@Facundo_Rodriguez_La here is some recent code for dealing with aggregation of variables from multiple sub process instances (usually from call activities)