Treasure Chests

What version are you using. In the betas theres this great "Chest" combo type, but in 2.10, you have to make the tile a "Slash->Item" flag, and set your undercombo to an open chest.

In 2.10 And Under: (Or Over, as this still works in any version.)

Make (Or Use a pre-existing) Slash->Item combo, then set the Room Type to be Special Item, then set the Special Item (Underneath Room Type on the Data Menu.) to be the item you want in the chest, then place Flag #10 on that Slash->Item combo.

Next, click on the combo that you want the Slash->Item combo to be replaced by when it opens to reveal the item, then go to Data-> Undercombo, and click "Set."

In the betas:
Create (Or use) a Treasure Chest combo. Make the combo directly after the Treasure chest combo (On the combo page, not in the game world.) what the chest will be when it's opened. Place Flag #10 on it and set the room type to special item and set the special item as described above.

Remember flag #10 doesn't work as inherent, unless it's already fixed in the 16's