How to make a multi OSX bootable USB / External Harddrive

Step 1: Erase and part the disk (I am doing command line just because its easier for me, you can use disk utiliy, just make sure its set to GTP and JHFS+)

I put sudo in all the commands that need root - You should simply run this as root to avoid having to put the password everytime. 

# This will list all your drives so you know what to replace /dev/disk4 with
diskutil list

# This will erase the flash disk or the NVME or w/e drive you choose to use (Make sure to get the correct one from the command above)
sudo diskutil erasedisk free JHFS+ gpt /dev/disk4

# This will create 6 seperate GPT partions for each install again change disk4 for your drive
sudo diskutil partitionDisk /dev/disk4 gpt \
    JHFS+ Install_MacOS_Big_Sur 20G \
    JHFS+ Install_MacOS_Catalina 20G \
    JHFS+ Install_macOS_Monterey 20G \
    JHFS+ Install_macOS_Seqoia 20G \
    JHFS+ Install_macOS_Sonoma 20G \
    JHFS+ Install_macOS_Ventura 20G


# This is where we actually install each version of OSX onto each part.
# I found removing the spaces from the downloaded media easier but you can do as you want
# https://github.com/ninxsoft/Mist - This is the tool i used to download all of the OSX installs direct from apple

sudo Install_MacOS_Big_Sur.app/Contents/Resources/createinstallmedia --volume /Volumes/Install_MacOS_Big_Sur --nointeraction 
sudo Install_MacOS_Catalina.app/Contents/Resources/createinstallmedia --volume /Volumes/Install_MacOS_Catalina --nointeraction 
sudo Install_macOS_Monterey.app/Contents/Resources/createinstallmedia --volume /Volumes/Install_macOS_Monterey --nointeraction 
sudo Install_macOS_Seqoia.app/Contents/Resources/createinstallmedia --volume /Volumes/Install_macOS_Seqoia --nointeraction 
sudo Install_macOS_Sonoma.app/Contents/Resources/createinstallmedia --volume /Volumes/Install_macOS_Sonoma --nointeraction 
sudo Install_macOS_Ventura.app/Contents/Resources/createinstallmedia --volume /Volumes/Install_macOS_Ventura  --nointeraction 

If you found my guide helpful and you would like to send a small donation - https://www.paypal.com/donate/?hosted_button_id=3YV2BWQRN6YF8

Hope this helps people.