In a model where a station provides multiple goods, suppose I use a loader to connect a chest and a cargo wagon.
chest -> loader -> loader -> cargo wagon. Two Loaders are used.
Only the first Loader is controlled by the signal. When the first Loader is closed, the train leaves, but there are still several items left on the conveyor belt between the two loaders. This will cause the next car to mix several different items.

So, can we add a signal so that after the loader is closed, the train will wait for a few seconds before leaving, waiting for the items on the conveyor belt between the two loaders to be cleared.