Is it possible to modify the files of the macOS Catalina installer to not require the admin password on install? For example changing a plist or editing an executable.
MacOS Catalina installer customization
installsoftware-update
Related Solutions
Drag-drop installs can go to an Applications folder at the root of the user's home folder and function without issue, but Adobe has been known for needing hooks in various parts of the OS. For example, a cursory overview of that package shows it wants to install certificates, the flashplayer plugin if not already present, etc. Conceivably, if you could 'snapshot'(using fsevents/dtrace/packaging tools like packagemaker or Composer, etc.) the installation in a VM and track down all the files it sprays on disk, and relocate those wherever applicable to the user folder on your system, AND the Air runtime and App in question could run without failing due to expecting to see resources in hardcoded directories....
In other words, magic 8-ball says 'highly unlikely'.
Massive bump to @IlyaB, I was stumped trying to get the full 5gb Install MacOS High Sierra.app but was stuck with the 19mb stub version.
My Process to get a working app that is currently making my bootable USB for High Sierra
1: Go to Mac App Store and download High Sierra (the 19mb stub)
2: Click Continue in the installer app once it downloads
3: Choose your boot disk (or any disk that has space)
4: Allow the installer to download (this is the contents of the missing "SharedSupport" folder within the installer stub)
5: The installer will prompt you to restart after finishing the 5gb download, at this point quit the installer and do not restart your system!
6: Go to your root (or whichever location you chose in step 3) and find the folder "macOS Install Data"
7: Copy the contents of that folder disregarding .DS_Store 
(9 files, folders, dmgs, pkgs, and plists)
8: Go to your Applications folder where the Mac App Store downloaded the stub version of "Install macOS High Sierra"
9: Right Click on that file and "Show Package Contents"
10: Within the Contents folder, create a new folder called "SharedSupport"
11: Paste the files you copied earlier from the installer download
12: And you're done! You should have a fully functional Installer file for bootable USB drives or just copying to other systems whether they be offline, or you just don't want to download the installer over and over.
I am currently in the lengthy process of creating a bootable USB drive to make a Coffee Lake i7 8700k Hackintosh build. I'm following this guide with the recommended motherboard. I'll try to update here with my success/ failure.
Best Answer
Yes, you can edit it but It won’t pass validation.
Most people script their modifications to run post install. Same with scripting things do run without prompting.