I've just figured how to use this, and it really makes things easier. BUt what about in missions. What I'm saying is will scenery added with the built-in editor explode if I bomb it or shoot at it?

Any scenery that you build using the built in scenery editor will appear in mission scenery but will not explode. So if you build a scenery at an airfield and then run a mission at the same airfield,you will have both sceneries jammed into the same space.Hagar is right in that can really kill your frame rates if your comp is marginal.There is an excellent tutorial by Nuno Mendes in the help/tutorial section on how to use the built in scenery editior.If you dl some other library objects bgl's like Rapheal Garcia Sanchez's D-daylib.bgl you can actually add more objects to the stock scenery editor but it takes some experimenting to see which ones actually will work because some objects will and some won't.The stock scenery editior also works well in conjuction other scenery design programs like Airport 2.60 or 3.0 or FSSC. Good luck