Let’s see if I can phrase this correctly. I used to know how to do this but cannot remember how.
I would drag a shape from Illustrator to Photoshop while holding down a key. When it landed in Photoshop it would be a path and I could create a custom shape. For the life of me I can’t remember what key I held down and even the great Google can’t seem to help. Does anyone know how to do this?
I wouldn’t drag anything between softwares as bad things can happen.
If you copy the shape in Illustrator, then paste into Photoshop, it will ask you if you want it to be a vector Smart Object. Say yes.
I’m not entirely sure what you’re asking, but you can copy something from Illustrator and paste it into Photoshop. When pasting, one of the options is to paste it as a path, which is editable (awkwardly so, in my opinion) as a vector shape in Photoshop.
I don’t know how to address your question about the drag-and-drop affair, but as already covered, you can paste an Illustrator path on your Photoshop canvas. Then, with the pasted path selected in the Paths panel, choose Edit > Define Custom Shape… Name the shape.
After that, choose the Custom Shapes tool and drop the Custom Shapes menu from the Options bar to see the available custom shapes, including the one you defined.