Map Help?

If I add a whole bunch of props to a map, can I save that place as a map? like, I added alot of props to portal level 19 to make it look like level 19 when aperture was still running, and i want to save it as a map so it doesnt get overwritten eventually.

Only way to save stuff as a map is to use Hammer.
There are no way to save something as a map in Gmod, I recommend learning Hammer if you wanna modify / make maps.