The DLC button has nothing to do with the workshop, it just was added with the same version.The DLC button on the other hand seems to be broken. Like I said it just opens the last location you imported from :S
What it does is to open the folder for PURCHASED steam DLC - if you haven't purchased any of the steam DLCs, then it goes to the last opened folder. But if you have purchased Steam DLC's, it's a shortcut to get those imported (instead of having to manually go to the steam folders).
I made the same wrong assumption that it was something for the steam workshop first, until I was corrected- and since I used the current steam sale for one DLC, the button now works for me as intended.



