question

There isn't a priority control for the tasksequences. Generally each item to transport creates a single transport job. This is a trasksequence. The tasksequences have got a break task, which is responsible for loading more than an item if there is still transport capacity in the taskexecuter (Crane). The tasksquences are executed by priority and rank in the tasksequencequeue node. You can change the priority of the tasksequences and this will lead to a different order of execution.

You want to unload all loaded items. Then the crane is allowed to load items again. Then you must change the priority of the tasksequence, that is responsible for loading an item, so the unloading is by priority. The priority must be higher than the not-begun-transport-tasksequences. You change this by source code in the OnLoad trigger of the crane.

treenode curTS = gettasksequence(current,0); // currently active transport TS
setpriority(curTS,getpriority(curTS)+1); // increment priority

Additionally if you want to unload all items at the same unload station, you find a picklist option in the OnUnload trigger that will do this:

Unload all items intended for this station before unloading to other stations

This will mix up the order of the loaded items of the Queue_Out, but the crane won't travel between RejectTray_Combiner and PassTray_Combiner so often.