wrong place.
Open UserDefinedTable.ascx.vb, line 577:
Actions.Add(GetNextActionID, Localization.GetString(Entities.Modules.Actions.ModuleActionType.AddContent, LocalResourceFile), Entities.Modules.Actions.ModuleActionType.AddContent, "", ResolveUrl("~/images/add.gif") EditUrl(), False, SecurityAccessLevel.View, True, False)
You need UDT Source, VS2003 andDNN3.x to compile a new version.