Installing older macOS version on external drive from current macOS version.

I'm trying to create an external drive where I can use to boot my iMac (currently on Sonoma) to Ventura or Monterey. I need to be able to test software on these older OS versions. The problem is that I have my external driver partitioned and ready to go, but when I run the "Install macOS Ventura" app, it tells me I can't install that version from Sonoma. Is there a way to run it from the console with flags that allow it to install?