Hernan. I didn't reply earlier as I'm no expert on this subject. I can remove a complete airport but that's as far as I go. The guys on the FSSC support forum know far more than me.
As you know, you can do this by manually adding an Exclude switch to Scenery.cfg.
Quote:what follows, is it: all, or items, or objects?
objects would remove scenery objects like default buildings. With this method it's sometimes difficult to be accurate enough to remove individual buildings. In FSSC I think it would be easier to use the Exclusion feature. Right-click/New Misc Object/Exclusion brings up this options window.
Check the Visual Scenery option to remove buildings. You can resize the Exclusion area & position it as necessary.
PS. Think I misunderstood your question. Most 3rd party scenery includes instructions for adding the Exclude switch if necessary. It's usually a matter of copy/pasting the full Exclude= entry from the Readme file into Scenery.cfg.