Yes, in general. In short, regarding the laws of Muktzah, objects are classified into three categories: utensils (which are defined as objects which have a permitted use on Shabbos), food, and all other objects which are not utensils or food (e.g. straw, rocks, dirt). If a person specifically designated an object to have a permitted use on Shabbos (e.g. straw to be used as a pillow) then it is considered a utensils as far as Shabbos is concerned and is no longer Muktzah.