There’s no need to clutter your Inventory with Gems in Diablo 4. You can leave all Gems in your Stash and you’ll still have access to them while combining Gems at the Jeweler.
Similar to how Crafting Materials worked in Diablo 3, you can save valuable Bag space and leave all Gems in your Stash because when you’re creating better gems by combining the lower-quality ones, you do not need to have them in your Bags.
Source: Reddit
