I really had to get used to this as well.
Tooll isn't like most of the 3d apps, where you open a file to work in it, but once you started it, it's more like a desktop of an OS.
So when you start it, you kind of see your desktop and you can just start making your demos there. But of course it get cluttered after a while. So what you will want to do is create "folders" where you can sort your nodes in.
For that you just select what you have created, right click and select "combine". Then you can choose a name.
When you click "ok".
All your nodes will be inside this new node.
You can then navigate into it with a doubleclick, or out of it if you use the "filepath" on the top.
Notice how every demo is combined in one of those groups or "folders".
It takes a bit of time to get used to it, but after a while it's really neat having all of your projects always available in that kind of "desktop" environment. And since all of the projects / scenes are really really small, it doesn't matter.
So behind that, tooll has to save all the projects somewhere of course. So if you want to find those files, you have to go to the "operators" folder in your "tooll2" folder and you will find a lot of files with random names.
Sort by date and you will see what tooll saved last. If you started your project right on the desktop then you will see that this one "desktop-file" got really big.
Everytime you "combine" something like I explained above. Tooll will create a new file with a random name.
The random name is handy because you don't have to care about the name or worry about creating duplicate files... but it sucks if you want to find your project really quick. If you open one of the operators with a text editor, you can find the name inside of them.