Create a boot image file from a Bootable USB Windows 10 install

I do not follow what you mean. The iso is just a container like a zip file containing all the boot files. What are you trying to do?

John,

As a different slant on this & in the hope of being helpful -

You can create a bootable ISO using the Media creation tool [from which you would create a bootable installation USB if you needed one].

Any existing installation USB you have will be at whatever Windows 10 version it was made from but by getting a new version of the Media creation tool as new Windows 10 versions are released, you can create new installation USBs at the latest version and you can use them for clean installations, updates & 'repair installs' / 'in-place upgrades'.

As long as Settings, Updates & security, Activation shows that you are activated with a digital licence & that you always make sure you are installing the same Edition [Home / Pro], you can reinstall to your heart's content and will be re-activated when you next go online without any action being needed on your part.

Denis