I must have known this at some point, but I’d obviously forgotten because I have a clumsy method I’ve used for years when I needed to copy selection outlines between documents. If this little tip saves anyone those extra steps, then revealing my personal ignorance was worth it.
Source: This is one of those little details I picked up during Jason Hoppe’s 5-Week Photoshop Fundamentals course. For as long as I’ve been using these tools, I still learn something new from almost every course I sit in on.