In Tools > Locks on the Wardrobe web page you can lock individual folders in the "Folders" tab.
There is currently a proposal in the suggestion box to add a lock action to individual items. Feel free to vote for it. It sounds like that is more like what you're looking for?
When the proposal gets implemented (it already has a good number of votes), I'm thinking of removing the locks tool (in Tools > Locks) in favor of the per-item lock action.