Whenever you create a new layer by clicking on the Create a New Layer icon at the bottom of the Layers panel, it will always appear above the currently active layer. I don’t know how many times I’ve seen someone create a layer and then drag it below the existing layer. You can save yourself a step by holding down the Command (PC: Ctrl) key as you click the new layer icon to create a new layer below the currently active layer.
This tip previously published in Colin Smith’s Photoshop Tips column, in the March, 2019 issue of Photoshop User magazine.