https://www.gamespot.com/articles/destiny-2s-big-20-update-patch-notes-weapon-slots-/1100-6461434/

With the big Forsaken DLC expansion drawing close, Bungie has released a major Destiny 2 update (as well as a Forsaken launch trailer). Patch 2.0 is now live and makes sweeping changes to certain areas of the game before the DLC launches. While some changes, like the overhaul of mods, won't come until the expansion hits, the patch does completely rework how weapon slots work, among many other things.