If I'm reading the original question correctly, this isn't about creating images for use in VMs, but rather is a request to be able to modify the harvester installer ISO so that it would include all the necessary configuration options required to install harvester automatically. I don't believe we have a procedure or anything documented for this, but given a lot of the harvester config can be specified as kernel boot arguments, I suspect it might be possible to use xorriso somehow to rewrite the grub config in the install ISO to include your desired configuration.
@fresh-waiter-942, are you able to open a github issue for this (
https://github.com/harvester/harvester/issues/new/choose)? It's probably a bit similar to
https://github.com/harvester/harvester/issues/5385 but isn't exactly the same thing, because that issue is focused on automating ISO install when running harvester virtualized for testing purposes, and I assume you want to deploy on real hardware.