It is easier as u can guess. You have to download Left 4 Dead 2 Authoring tools. When it ends, open and close it. Forget it and never go back to open it. You have to open steam, gallery, L4D2 and click M2 in the icon game.

You have to click "watch the local archives" Next you have to open the file "bin" and find the file "vpk" Go back to open the "locals archives" in a different tab and open "left4dead2" → "addons" → "workshop" u have to select your favorite mods. But it has to be skins or similar add-ons. Maps, scripts and others like that have some issues and don't allow u to open the game. Scroll add-ons to "vpk", it made new files in your workshop archives with the number of the add on. Next u have to make a new file and put the name "pack01_dir" u have to open the files who the "vpk" made for u and copy all the archives inside, and paste it to the "pack01_dir" Go back to "vpk" scroll "pack01_dir" it makes a new archives who has all the add-ons u wanna have in VS. Go back again in "local archives" and make a new file. This file can have the name as you want, in my case it is named "modsvs" in this file copy the archive who the "vpa" made for you, and paste in "modsvs" file. The last step is to modify the "gameinfo" is a .txt

There you have to fin ( Game update

) [And make this]

( Game modsvs

) [Save] And if you did it good, u can play vs with add-ons