I operate a multi-boot setup for various reasons. However, rebooting into a different operating system is not exactly an enthralling activity.
On Mac hardware, you can hold down the Option key at startup to launch a boot picker. But, in fact, this is the only supported way to boot most standard UEFI firmware—macOS has a "startup disk" picker, but it can only detect installations of macOS and Windows, leaving our beloved Linux behind. BootList fills this gap by allowing you to select any entry in your EFI boot menu (stored in NVRAM) to boot from on the next reboot (by setting the BootNext variable in NVRAM).
BootList is currently only on macOS, but there is no good reason not to port it to other platforms too (so I may do that sometime).
BootList was hacked together as a quick'n'easy solution, so it relies on the wonderful bootoption command-line tool to do the heavy lifting. It should be installed in /usr/local/bin, e.g.,
brew install bootoption
Once the app is up and running, usage is simple as long as you know the rough layout of your boot menu. I recommend using bootoption proper to get more detailed information about this where appropriate.
Boot menu entries are parsed from the output of bootoption list.
When you select to boot from an entry, a small snippet of AppleScript is used to elevate permissions (you will see a password dialog), as root access is required to write to NVRAM. The temporary shell process spawned by AppleScript runs bootoption set -x <bootnum> to set BootNext in NVRAM, which is read by the Mac bootloader as the default operating system on next boot. The system then reboots normally.
I built the GUI with SwiftUI, both as a learning opporunity and so that I could get it done quickly. This means that, unfortunately, the app requires macOS 10.15 or later.