Adding permanent props to a map?

I want to do this ingame, not by using Hammer or a map editor. Is this possible?

Advanced Duplicator 2

Any other way? Someone said ‘creation menu’ but I don’t know what he means.

The Context Menu (Default C) > Right Click on an entity > Make Persistent.

I tried what you said (With the Make Prop Persistant option) and when i leave and come back, it is gone…Not sure why this is happening

It might be a prop protection addon that removes the props players spawn when they disconnect.

Yeah, your probably right, but i’m not willing to turn off the option “Clean Up Disconnect players entities” just for this.