Forum Display Enhancements - Different Smileys for Different Styles

I don't know if this has been posted before, couldn't find anything specific using the searches.

Anyhow, I've found a super simple way to have different smileys, depending on the skin in use.

I.E. I've created a "Work Safe" skin, which replaces my otherwise red smileys, with subtle grey ones.

Copy your old set of smileys, and copy them to a new folder within your Images folder. Now, either edit the smileys you wish to change etc.

Find the path to your smilies folder, I.E. www.yoursite.com/forums/images/smilies

Go to "AdminCP" > "Styles & Templates" > "Replacement Variables Manager"

Now click on "Add new replacement variable" next to the style of your choice.

Where it says "Search for Text " enter the path above, I.E. "www.yoursite.com/forums/images/smilies and where it says "Replace With Text" change the "smilies" folder to whatever you've called your new smileys folder.
I.E. "www.yoursite.com/forums/images/smilies_newstle"

Super simple

[Moooooon]

Hmmm... doesn't work for me :-/ Is this 3.7 specific? I am running 3.6.10 and it's not replacing anything. Do I have to enable this feature somehow?