Re borer on Shabbos, if there is a packed drawer, and within that packed drawer there is a box of identical items, such as sandwich bags, would it be considered borer to take one of the sandwich bags from the box and use it for later? Note that nothing else was moved in order to reach the box of sandwich bags, and the box itself was not overlapping anything else, but other items in the drawer are overlapping each other. Please could you clarify if this note makes a difference to the answer and why/why not.
Before answering your question, let me ask you a different question. If the box was not mixed in the shelf, would it be permitted to remove some of the bags, from the box, to use for later or are the bags mixed with the box? They are not considered mixed with the box, because a container is not considered mixed with the items that it contains. Therefore, we look at the bags in the box as if they are not mixed with the box. The fact that the box itself is mixed with other things, does not affect the bags, because they are in their own place. Since they are not mixed with the rest of the shelf, it is permitted to remove them on Shabbos.
The fact that you don’t have to move anything else in the drawer, is also helpful, as now you don’t have a muktza issue, if there were muktza items in the drawer.
איל משולש (בורר) פ”ד סע ל”ט.