Try using ventoy, It's a fantastic piece of software
You can install it to anything, thumbdrives, external hard drives, internal hard drives, SSDs, HDDs, it don't mater
Just download the windows package, and launch the "Ventoy2Disk.exe", your 250GB drive, if plugged in, should show in the list, here's a quick guide from the website
After you install it you'll see 2 different devices for that same drive (it creates 2 partitions) one should be named "VTOYEFI" which is the actual application, you don't have to mess with it, the other should be named just "Ventoy"
This Ventoy device is basically just empty space you can use for whatever, and there should be a folder named "Isos" in there, if there isn't just create one, I honestly can't remember if it creates it automatically or not
Then just drop the isos for whatever you want to boot from in that folder, no need to burn them to the drive
That should make it bootable
you don't necessarily need to change boot options, the great majority of motherboards will have a "Boot menu" option at boot, these options show for a short time whenever you boot your pc right at the beginning, using this boot menu option you'll get a list of all the bootable devices from which you can choose, without changing the boot order.
Though if you have "fast/ultrafast boot" or the like enabled in your BIOS/EFI setup you'll need to change that
Try using ventoy, It's a fantastic piece of software
You can install it to anything, thumbdrives, external hard drives, internal hard drives, SSDs, HDDs, it don't mater
Just download the windows package, and launch the "Ventoy2Disk.exe", your 250GB drive, if plugged in, should show in the list, here's a quick guide from the website
After you install it you'll see 2 different devices for that same drive (it creates 2 partitions) one should be named "VTOYEFI" which is the actual application, you don't have to mess with it, the other should be named just "Ventoy"
This Ventoy device is basically just empty space you can use for whatever, and there should be a folder named "Isos" in there, if there isn't just create one, I honestly can't remember if it creates it automatically or not
Then just drop the isos for whatever you want to boot from in that folder, no need to burn them to the drive
That should make it bootable
you don't necessarily need to change boot options, the great majority of motherboards will have a "Boot menu" option at boot, these options show for a short time whenever you boot your pc right at the beginning, using this boot menu option you'll get a list of all the bootable devices from which you can choose, without changing the boot order.
Though if you have "fast/ultrafast boot" or the like enabled in your BIOS/EFI setup you'll need to change that