Ventoy
https://www.ventoy.net/en/index.html
It's not just a bootable USB creator, it's a bootloader. You drop images in and it automatically will display them in a boot menu for you.
What I was dreading was either having to buy another USB stick, or having to sacrifice (well, not permanently) my good $100 Corsair one for a boot image. I will have to tear down the partitions and create one for this (I'm assuming) but once I get the device all set up again, it will remain in place. Need to boot something else? Drop it in.Ventoy is an open source tool to create bootable USB drive for ISO/WIM/IMG/VHD(x)/EFI files.
With ventoy, you don't need to format the disk over and over, you just need to copy the ISO/WIM/IMG/VHD(x)/EFI files to the USB drive and boot them directly.
You can copy many files at a time and ventoy will give you a boot menu to select them (screenshot).
You can also browse ISO/WIM/IMG/VHD(x)/EFI files in local disks and boot them.
x86 Legacy BIOS, IA32 UEFI, x86_64 UEFI, ARM64 UEFI and MIPS64EL UEFI are supported in the same way.
Most types of OS supported (Windows/WinPE/Linux/ChromeOS/Unix/VMware/Xen...)
1100+ image files are tested (list), 90%+ distros in distrowatch.com supported (details)
This sounds great on paper, I'll have to get playing with this ahead of time. I would think though, I'll have to set it up for MBR booting for testing now though and redo it for UEFI. I can't see it supporting both boot methods (the low level bootstrap part I mean) at once (but I haven't read much yet).
There's binaries for Linux and Windows, and source code for moi