To make a USB stick which can boot multiple ISOs, use Ventoy. Ventoy is an open source tool which creates a special USB stick. That stick contains an exFAT partition in which you can copy multiple ISO files and an EFI partition where Ventoy puts its bootable menu. When you boot on the Ventoy USB stick, the menu lists all the ISOs you placed in the exFat partition and you can boot any of them.

Go to the Ventoy release page to find the latest version of Ventoy.

cd ~/Downloads
wget https://github.com/ventoy/Ventoy/releases/download/v1.0.91/ventoy-1.0.91-linux.tar.gz
tar -xvzf ventoy-1.0.91-linux.tar.gz
cd ventoy-1.0.91
sudo ./VentoyGUI.x86_64

Bash script to check for and download latest ventoy version then start it. Requires wget, curl and jq:

ventoy-update.sh

#!/bin/bash

get_ventoy_release() {
curl -s https://api.github.com/repos/ventoy/Ventoy/releases | \
  jq -r '[[.[] |
    select(.draft != true) |
    select(.prerelease != true)][] |
    .assets |
    .[] |
    select(.name | endswith(".tar.gz")) |
    .browser_download_url]' | grep -o "http.*-linux.tar.gz"
}

VTDLURL=$(get_ventoy_release | head -1)
VTFILENAME=$(echo "$VTDLURL" | cut -d "/" -f9)
VTDIRNAME=${VTFILENAME::-13}
if [ ! -d "$VTDIRNAME" ];
then
    if [ ! -f "$VTFILENAME" ];
    then
        echo "$VTDLURL" | xargs -n1 wget
    fi
    tar -xvzf $VTFILENAME
fi

cd $VTDIRNAME
sudo ./VentoyGUI.x86_64
#rm -rf /tmp/ventoy

Choose the device which corresponds to your USB stick.

Press the Install button.

Once Ventoy is installed two partitions will be available on the USB stick:
1.) Ventoy - this is empty and is the majority of the free space to copy iso files to
2.) VTOYEFI - this is an EFI partition, not usually auto-mounted, which contains the Ventoy config files

The 'Ventoy' partition usually will be auto-mounted and can be used.

Copy ISO files to the stick.

Windows ISO files should be renamed to end with _VTWIMBOOT (e.g.: win10_english_x64_VTWIMBOOT.iso) to boot properly. Alternatively, CTRL+w can be pressed in the Ventoy menu to activate WIMBOOT mode.

Boot on the Ventoy USB stick.

The ISOs you copied should appear as bootable options.

All the plugins and their related files must be in a “ventoy” (all lowercase) directory in the first partition of the disk (along with the iso files and created by yourself). Directory and file names are case sensitive.

A json file ventoy.json must be placed under the ventoy directory (no subdirectory) as the configuration file. The file must match the syntax of json and the outermost layer must be an object( { } ). For json syntax you can check it with the 2 online tools as follows:

ventoy.json must in UTF-8 encoding.

VentoyPluson can be used to create and edit this json file.

sudo bash VentoyPlugson.sh /dev/sdX

This loads a web server and provides URL to use the editor via browser.
More details: https://www.ventoy.net/en/plugin_plugson.html

The “VTOYEFI” partition needs to be mounted manually if required or desired, e.g.:

sudo mkdir /mnt/vtoyefi
sudo mount /dev/sdb2 /mnt/vtoyefi/ -o rw,nosuid,nodev,relatime,uid=1000,gid=1000,fmask=0022,dmask=0022,iocharset=utf8,errors=remount-ro,uhelper=udisks2 

source: https://linuxmint-user-guide.readthedocs.io/en/latest/winiso.html

https://nixsanctuary.com/how-to-create-multi-boot-usb-drive-without-ventoy-grub-ftw/