The window closes. Your desktop remains unchanged. But the .rdr volume is gone. Ejected. No trace.
To install: double-click setup.rdr. To go back: you can't. The APFS snapshot will be taken of your soul, not your SSD. download macos high sierra 10.13.5 image file -.rdr-
: On an existing Mac, you can use the command softwareupdate --fetch-full-installer --full-installer-version 10.13.6 . Warning on Third-Party Images The window closes