I found this method elsewhere, and using the search function on the forums, did not find it posted here. I only found questions, but not many answers. Things you will need
SII Decrypt (Included as an attachment, but the original downloaded is also included)
Your original ETS2/ATS Profile
Some people here may ask, why do this? I mean, you can just use money/XP mods, whatever. Yes, you can do that, but if you're like me, you like a sense of progression. You can easily use an XP mod to progress, but where is the fun in that? A sense of progression feels important in slower-paced games like this, and having access to everything right away is ruining the experience a little. As well as the fact, you don't have to drive hundreds/thousands of kilometers/miles to unlock garages and drivers, so it is a little easier just to have this done. This way keeps your garages, starting city, drivers, trucks, XP, and purchased items intact.The only thing that may change is your money, and that's not in my control at all, it is the game server.
Find your profile that you want to duplicate. By default, it will be in your Documents/[Euro Truck Simulator 2/American Truck Simulator] folder. The profile will have a set number ID. If you can't find it (Because you have multiple profiles), then load ETS2 and start your profile, then drive for 10-15 seconds. Your profile will be listed as the most recently edited profile. Here is what mine looks like. You may have more OR less files than I do in your actual profiles. This is normal.
To get started, we need to create a new profile. In this example, it will be called "Multiplayer", but it can be whatever you like. You must be able to remember this name, as this cannot be changed, and you must know the profile name exactly. The rest of it does not matter, as it will be replaced later on. Here is my original profile and my new one. The only thing that will matter here is the name, and you can put random values in the other options. When you create the profile, run yourself through the setup wizard, as I am not sure if the controls carry over. I personally have not tested. Opt to skip the tutorial, and skip the intro movie. Once you are in your truck, save and quit the game.
In your profiles, the newly created profile should be there. Open the new profile, and marvel at the fact that you are about to murder those poor files. Then send them to the graveyard. The desolate place known as the Recycle Bin, often foretold among the files as horror stories and fairy tales. Now laugh as you realize, files are not sentient, and I just made this tutorial a little more interesting for everybody. Or are they?
Go to your original profile (The one you are duplicating), and copy the files. Paste them into your new profile folder. Step four is easy.
In your new profile's folder, there should be a file named "profile.sii". This is the file we will be using. If you open it with a text editing tool (I am just using notepad), you will get a random bunch of letters. This is because the profile is encrypted, and we will need to use SII Decrypt to view it properly. If you haven't already, download and extract SII Decrypt. This is an extremely useful tool, and this would not be possible without it. Once you have SII Decrypt extracted, open the folder, but not the .exe. SII Decrypt is a command line based tool, which is a fancy way of saying you need to drag your profile.sii file onto your SII_Decrypt.exe. If done correctly, a transparent window may open for less than a second, and in some cases nothing will happen. If it worked properly, it should have actual values when it is opened up in Notepad or other text-editing tools. NOTE: You do NOT need to do this to your profile.bak.sii file, and I believe it is safest not to do it. You can always recover the backup and re-do this. Here are the images used in this step.
Now that you are here, scroll all the way to the bottom, and find the value "profile_name". In my case it is dwcuyle, but it will be the same as your original profile. Set that value to the same name as the profile you created. In my case, it is "Multiplayer". It is case sensitive. Save the file (CTRL+S or File and Save), and close notepad. Here are the images in this step.
Now you can load the game. If done properly, all of your stats will match your SP. Garages, trucks, starting city, literally everything will carry over. Now, you may enjoy the usage of all of your XP, all of your trucks, all of your garages, and everything you had, carry over! The money will not carry over though. Not because this method is flawed, but because the server time is different so you will spawn with several millions of dollars. At least you would if you had one driver before this. If you have no drivers, the money will be fine.
Credit goes to Sniper for creating this amazing tool and publishing it on the SCS forums
Credit to bazztard84ger to finding this method and posting it on squirrel.tv
Credit to me for updating the tutorial/programs, and adding more information per step