Since the new stockpile mechanics, the pawns are generally good about filling-up partial stacks before starting another, though it isn't perfect. I recommend that a job withing hauling be created with a lower priority than actually hauling that simply reorganizes the stockpiles to combine any partial stacks and free up room. This mostly has to do with meals, as I generally have several partial stacks of meals.
Also, as a second idea, if pawns could try to choose partial stacks to use up before full stacks that would be great. That pile of 12 squirrel meat in the back corner is taking up precious room that my extra stacks of 75 potatoes could use.
Maybe part of the reorganization of stockpiles could include putting partial stacks towards the edges of the stockpiles, where they would more likely be used.
I heavily support this idea I kind of hinted at the last time we discussed it.
I would call it the "must stack" job. Low priority, a colonist would scan the stockpile and stack anything that can be stacked.
Myself I wouldn't really need more.
New Trait: OCD