I have noticed this (what appears to be a) "tagging" or label option (image below) available in my Marketing Cloud instance on the Journey Builder page, but it seems to be greyed out. I have investigated the various ways (security options, journey configurations, etc.) to make it available to my users and me but have had no success (e.g. is there a way to tag/label respective journeys and then filter on those tags/labels). As far as I am aware, this feature is/was not available. Am I missing something totally obvious as it relates to this button? Has anyone else had any success in utilizing this?
Answer: Missing something totally obvious. (big eyeroll and cue more coffee) :-)
There is a checkbox to the left of each journey. Once selected, you can then specify a tag (or tags) for the journey, etc. (Screen shot below).
In other news - I did see, there was an update today (3/29/18) from a product manager on this idea (Create folder structure in Journey Builder): https://success.salesforce.com/ideaView?id=0873A000000E4xvQAC that folder structure for JB was in development and planned for the June MC release.
Just wanted to share an update on this topic - since I had posted it some time ago. Journey Folders (Folders for Journey Builder) will be in the June release (June 23) for Marketing Cloud. Just an FYI for anyone who's anxiously been waiting for this feature!