I heard that the stores in settlements generate caps and that you find them every so often in the workshop menu under "misc" but when I go to my workshop menu there is no misc category, or any category for that matter, its just my inventory and the workshops inventory and no caps. I have 10 people at my settlement and the shop has a person assigned to it and I've waited 2 game days.

To change category, use left and right. It will cycle through weapons, armor, misc etc..