The bootloader will scan all partitions and find one with the Haiku GUID and a kernel in it. So there is no need for manual configuration.
The integration of the bootloader in beta 3 was a bit experimental. Since then, the Haiku install disk comes with an EFI partition, and the file inside that is named BOOTX64.EFI. And you can mount that partition from Haiku to do the copy of the bootloader. So, it is a bit simpler than it was before. It still is not perfect, ideally, BootManager should help with setting up a boot menu on EFI systems. But someone has to write the code for that.