The Easiest Way to Create Your Own Multiboot USB

If you're a system administrator, it's a good idea to have a multiboot USB pendrive so you can install an operating system, back up or restore the computer, and (if necessary) boot to a live system.

To create a multiboot pendrive, you need three things:

Computer (Windows or Linux based)
4GB or larger pendrive (USB 3.0 recommended), I use a Kingston 128GB USB3.0
Software to format and handle your iso files

I have tried making my Multiboot USB with Rufus, YUMI, MultiBootUSB and WinSetupFromUSB. None of them work well.

My goals were:

Freeware (open source)
Manage Windows and Linux based iso files
Works on BIOS and UEFI based PCs
Easily modify/replace existing items on the Pendrive
Use NTFS or exFAT, because I'd like to copy larger files than 4GB to Pendrive

After one day's research, I found the Ventoy software, which does all of them very well. Just install the software on your pendrive, then copy your iso files here. That's it. It will automatically recognise all your iso files, then you can boot from them. There's no need to uncompress, it works without. Sounds crazy, right? It is, but it works.

Let's see how to do it on Windows PC.

Make your Multiboot USB in 5 steps

Download the Ventoy software from the official webpage (the version may be different, download the latest one)
Uncompress the downloaded file, then run the "Ventoy2Disk.exe" file as admin.
Select your Pendrive (make sure that you don't have any important data on this one!), then press "Install"
Confirm the formatting twice, then wait a few seconds
You're done! Now, simply copy iso files to Pendrive, and you're ready to go.
Optional: if you want to modify the theme, follow this guide. If it seems too complicated, leave a comment below, and I'll extend this article with this info as well. The default theme looks like this:
After changing the theme, you can do something like this:
GRUB themes are available here for free.