How do I change the icons and labels in the MacOS boot manager? I freshly installed Big Sur with Windows 10 Boot Camp on a late-2013 MacBook Pro Retina with a replaced SSD. When I hold down the option button at boot, the options are listed as &quot;EFI Boot&quot; (Windows 10) and &quot;Macintosh HD&quot;, but both are using external drive icons instead of internal. Under MacOS, the icons for both drives appear correctly as internal drives. I tried changing drive names in diskutil, renaming the drives in the MacOS Disk Utility and under Windows, placing .VolumeIcon.icns files in various places, and various bless commands.
I'm asking this to answer my own question, I couldn't quite find a correct solution in any one spot. Pay close attention to the folders involved, this was the important part.
Rename “EFI Boot” in Startup Manager:
Open up a Terminal and use the following commands:
diskutil list - use this to find the Windows EFI partition
sudo diskutil mount disk0s1 - whereas &quot;disk0s1&quot; is your EFI partition
sudo bless --folder /Volumes/EFI/EFI/Boot --label Windows - whereas &quot;Windows&quot; is your label of choice
Rename “Macintosh HD” in Startup Manager
Similar to above, but:
sudo bless --folder /System/Volumes/Data --label MacOS - whereas &quot;MacOS&quot; is your label of choice
Missing/Wrong Boot Manager Icon
Reboot in recovery mode (command+R at boot) and use a terminal to run
csrutil disable
… which disables SIP protection
For Mac side:
sudo cp /System/Library/Extensions/IOStorageFamily.kext/Contents/Resources/Internal.icns /System/Volumes/Preboot/.VolumeIcon.icns
This will change the Mac/Macintosh HD boot icon to the default internal drive icon, but you can just copy whatever .icns file you wish to that location.  See other posts for info on making your own .icns files.
For Windows side:
sudo diskutil mount disk0s1 - Whereas disk01 is the name of your Windows EFI partition from above
sudo cp /System/Library/Extensions/IOStorageFamily.kext/Contents/Resources/Internal.icns /Volumes/EFI/.VolumeIcon.icns
Don't forget to enable SIP protection again, if you wish, by booting back into recovery mode and using:
csrutil enable