Most things can be copied from one document to another. Layers, styles, adjustment layers, paths, and more. It’s actually easy, but maybe not very obvious. Choose the Move tool (V) and, in the Layers panel, click on the layer or object you want to copy over. Drag it up to the tab of the document into which you want to move the asset. Keep holding, wait a moment, and the document will open. Drop the asset on the canvas and it will be applied to the currently active layer. If you’re copying over a layer, it will be added above the currently selected layer.
This tip originally published in Colin Smith’s “Photoshop Tips” column in the August, 2023 issue of Photoshop User magazine.