While the Brief description essentially covers the use of this, I'll elaborate here:

The zip file contains two script files.

a .bat (Batch) file, for windows, to copy everything on to a USB stick/drive, and a .sh (shell script) file, for Linux, to copy OFF the USB stick/drive and into the appropriate locations on the steam deck.

Note: Please confirm that your Profile in Vortex says "Game settings: No" on the profiles tab. If it says "Game settings: yes", the settings (.ini files and .txt files) may be stored in another location which can't be grabbed by my scripts and will need to be copied manually according to the installation procedures of whichever mod collection you are using, or will require the end-user to locate and copy manually.

Use:
Copy both scripts on to your USB stick, or USB hard drive.
Run the bat in windows, answer the prompts, and wait for the complete message.
Unplug, plug into your steam deck, and Run the shell script from the Steam deck Desktop mode. Wait for the complete message.

While the bat file is very noticeable in its copying, the Linux shell script will appear to be frozen. It's not, unless something terrible has occurred. Just let it finish.

It's recommended that you run this while connected to a dock, or some other device that will let you charge while you copy, just in case, and you can select from the "battery and brightness menu", bottom right, to "Manually block sleep and screen locking" mode.

Scrips are all in plaintext and annotated, if you would like to ensure that they're not trying to delete system32 or run "rm -rf --no-preserve-root /" (DO NOT RUN THAT COMMAND)

For troubleshooting, I'm generally found in the Steam Deck section of the Immersive Discord server, for the Immersive and Adult/Epic/Pure collections.

Edit: Say "No" to paid mods.