Welcome to the most open ended portion of the site, from here, the sky's the limit. I only know so much, but ill share what i know.
- Editing the HMworld.sav file So, you've been messing around in the player saves for a while now, but how about the world save? First, the only reason there is a world save-file is because of houses. whenever you leave a item in a house, the world saves it into this file for later. Now, it happens to work out that we can edit this file so that it loads new items into the world. In and out of houses. Heres an example of my HMWorld.sav Now, This is important : Because of the fact that it only saves items that have the furniture tag, and inside houses, every-time you restart the server, this file will be wiped so that no items that use to be outside the houses are loaded. So be sure to have a second copy of your HMworld.sav file to replace the wiped one. Also, because you replace the HMworld.sav file at every reboot, players who own houses lose whatever items were in here (If you don't understand well anything above this, this probably means you aren't ready to be looking around in here)
But, the possibilities for what you can place into this file are almost limitless.
You can use this list of Variables to find some things to add to your save. Note that alot of theses items aren't useable in the HMworld.sav but they maybe useable in conjunction to OTHER variables, player saves, and who knows what else.
Heres some tips on what i know
By removing the buy = x on a item, it will make it a sell point, although it will spawn a original copy of the item, not the original copy.
The only way i know to track coordinates is to count them manually. Place an item on a easy to remember spot, like 100,100 and walk and count how much you move form it to find your location of where you wish to place the object.
I have done small testing with NPC, it seems they don't place when i add them to the HMWorld.sav, But they can be placed while in a player save. By editing a NPC desc, makes them say what the desc says. (This is a prime example of how sometimes different objects make other variables function differently.)
I have also done some extensive testing on placing turfs. but I always get an error on attempt to load it.
If your out of ideas on what would cause an object to do something, get it in-game, and load the player save with it in it. It might give you what makes it.
Want to restrict an item to a single job? change JobR to the job you want to have it
Want to make it so only one player can buy an object? Change the players job to something unique, then change JobR to what the name of there job is.
Don't forget quotation marks (" ") where you need them in a save file, there is no faster way to trash a good HMworld.sav than to forget them!
Plus a whole lot more!, take a gander at my HMworld.sav, theirs alot for in there that im probably forgetting! Actually, if you figure out something that you would like to see added to this list, get a hold of me and ill add it (With proper credit added, of course)