Screen 83 is the dungeon template screen. Here you can set up default combos, etc. for the entire map.

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  In The Legend of Zelda, the dungeon rooms follow a standard template of four walls, each with at most one door. To ease the creation of NES-style quests,
 a 'dungeon template' can be made and applied quickly to a screen. 
  The dungeon template is made in screen 0x83 of the current map. 
Only the first two rows and columns of combos in layer 0 are used in the template.
  In a usable screen, choosing 'NES Dungeon Template' will let you place the template onto the current screen. 
You can choose to use a certain combo to fill the 'floor' of the screen, or leave the floor blank.
  Selecting 'Apply Template to All' applies the NES Dungeon Template to every screen in the map.