If you’ve built a custom Process Template you might have added some WorkItem types that the user should not directly interact with (such as Microsoft’s Shared Step type), you can now (as of TFS 2012) hide these types by adding them to the corresponding Category entry, namely “Microsoft.HiddenCategory”.
Microsoft has added the following by default (unless you migrated, then you might want to add them by hand, too):
<CATEGORY name="Hidden Types Category” refname=“Microsoft.HiddenCategory”>
<DEFAULTWORKITEMTYPE name=“Code Review Request” />
<WORKITEMTYPE name=“Code Review Response” />
<WORKITEMTYPE name=“Feedback Request” />
<WORKITEMTYPE name=“Feedback Response” />
<WORKITEMTYPE name=“Shared Steps” />