Whatever scene you are in, you can go to the file menu and click save as and rename your scene. That is how you copy and paste a scene, or duplicate a scene.
This is really handy when you want to branch out and try something new and you don’t know if it will work. Just make a copy.
Another really easy way to save your work is to export it in a unity package. You right click on your assets folder choose export package and then you choose the check boxes of what you want included. This is a really compact way to save your work but it doesn’t save tags I believe … .double check how it comes through by importing it tinto new project. This is also really helpful if you have a big asset pack Like that huge castle I got on unity Asset store and you want to split it up, You can just export the part of the assets that you’ll use. Then your project won’t take so long to open n whatnot.
I also use this to export my work when I develop a character and a script and all sorts of things and then I want to make it into a little package. No one explains this in any of the tutorials but it is a good idea when you back up your work. When you’re fully backed up you can create a copy to totally just play with and figure out what happens when you poke this or that.