SlenderVF

I’ve been watching a tutorial on Hammer and how to use it and in the tutorial it was demonstrated that you can copy an prop entity from one hammer map to another by simply copying and pasting it into the other map, however this simply doesn’t work for me. Granted, this tutorial is a few years old however I don’t believe anything should’ve changed inbetween then. Is there any way to enable this or transfer entity’s between sessions?