Mac Startup Manager configuration (MacBook Boot menu)

Apple Startup Manager - is a list of boot disks, that shows up upon reboot of an Intel Mac with pressed Option key.

Unlike other boot managers (GRUB, rEFInd), which are regular EFI boot loaders, it resides in the system firmware.

In order to configure it, there's a macOS command line tool called bless. This tool can also help restore macOS's .efi files on EFI partition, if those get corrupted for some reason.

"Blessed" means that system firmware will look such file/directory/partition for boot code.

Different things can be blessed:

If a file/folder is blessed, the partition volume header is updated with the path to such file or folder (so it persists if the nvram is cleared). A file/folder can be unblessed.
We can also bless a volume (mount mode) - this does not make modifications to filesystem, just updates the nvram.
We can configure firmware to boot from network (netboot mode), specifying protocol and server.

Before blessing any volume, we need to make sure it has a boot loader, for example [UUID]/System/Library/CoreServices/boot.efi (non T2 Macs with APFS) on the special Preboot volume /dev/disk1s2.

Other commands

bless (shouldn't be used anymore)

sudo systemsetup liststartupdisks and sudo systemsetup getstartupdisk (on T2 Macs requires disabling SIP)

Rename entry in Startup Manager

diskutil list - use this to find the Windows EFI partition sudo diskutil mount disk0s1 - whereas "disk0s1" is your EFI partition sudo bless --folder /Volumes/EFI/EFI/Boot --label Windows - whereas "Windows" is your label of choice

or, for Macbook entry, use the following:

sudo bless --folder /System/Volumes/Data --label MacOS

Other commands

Rename entry in Startup Manager

See also