BP capture works like the following:

Thread.sleep(5000) // wait before dumping profiles
(in app) Process.sendSignal(Process.myPid(), /* SIGUSR1 */ 10);
Thread.sleep(1000) // wait for profiles to dump
kill app

Jiakaiz@ suggested a way to make this work for multi-process by serially broadcasting to each app process:

Thread.sleep(5000); // wait before dumping profiles
for (var process : processes) {
  (in app) Process.sendSignal(Process.myPid(), /* SIGUSR1 */ 10);
  Thread.sleep(1000); // wait for profiles to dump
}
kill app

See internal convo