This scheme shows how NESmaker stores screen data in ROM upon exporting your game.
The ΔHEX values represent the data offset relative to where screen data starts.

ΔHEX   Description
00-77  Screen collision data
78     Screen type
79     Monster group number (TN)
7A     Palette data
7B     Sprite subpalette 1 (TN)
7C     First set of screen flags
7D     "ScreenByte01"
7E     Path information
7F     Warp-to screen
80     Warp-in position
81     Sprite subpalette 2 (TN)
82     "screenLoadTemps"
83-85  Untriggered day spawn locations for monsters 1-3
86-88  Untriggered night spawn locations for monsters 1-3
89-8B  Triggered day spawn locations for monsters 1-3
8C-8E  Triggered night spawn locations for monsters 1-3
8F-91  Monster group number (UD, UN, TD)
92-94  Sprite subpalette 1 (UD, UN, TD)
95-97  Sprite subpalette 2 (UD, UN, TD)
98-99  Monster table pointers
9A-9D  String group pointers (UD, UN, TD, TN)
9E-A1  Spawn locations for monster 4 (UD, UN, TD, TN)
A2-A5  Untriggered day IDs for monsters 1-4
A6-A9  Triggered day IDs for monsters 1-4
AA-AD  Untriggered night IDs for monsters 1-4
AE-B1  Triggered night IDs for monsters 1-4
B2     Song ID (#$FF for silence)
B3-B5  Unused, but intended for additional (un)triggered day/night songs
B6     Second set of screen flags
B7-BA  Sprite subpalette 4 (UD, UN, TD, TN)
BB-C3
C4     Tile layout settings ("tileLayout")
C5-CA  Background tiles to load
CB-CF  Sprite subpalette 3 (UD, UN, TD, TN)

* UD/UN/TD/TN = data for (un)triggered day/night screens


Additional information regarding (some of) these bytes:

00-77 Collision data  eeee oooo
                      |||| ++++-- collision type ID for odd metatile
                      ++++------- collision type ID for even metatile
      These 120 bytes contain collision data for the 240 metatiles, stored in
      high and low nybbles. To get the collision type for a certain metatile,
      take the metatile's location and divide by two (LSR) to get the
      corresponding collision byte, then take the high nybble if the metatile's
      location is odd, or the low nybble if it's even.
      [@TODO; clarify further perhaps?]

7D  ScreenByte01      xxxxxx ss
                      |||||| ++-- screen speed (afaik this is not implemented further)
                      ++++++----- unknown/unused

80  Warp-in position  yyyy xxxx
                      |||| ++++-- x-position on screen (in metatiles)
                      ++++------- y-position on screen (in metatiles)

82  screenLoadTemps   t sss xxx w
                      | ||| ||| +-- overworld (0) / underworld (1) screen flag
                      | ||| +++---- (unknown/unused)
                      | +++-------- game state (main game, win screen, ...)
                      +------------ 16x16 metatile (0) / 8x8 tile (1) screen flag

98  monster data      nnnn uuuu
                      |||| ++++-- untriggered day monster table offset
                      ++++------- night monster table offset

99  monster data      xxxx tttt
                      |||| ++++-- triggered day monster table offset
                      ++++------- unused monster table offset
    The high nybble of $99 should be used as a triggered night monster, but
    because of a bug this doesn't happen by default.

C4  tileLayout        $00   %00000000 = Double Main
                      $0C   %00001100 = Double Main (no hud)
                      $40   %01000000 = Main/Screen/Path
                      $70   %01110000 = Main/3x Screen
                      $7C   %01111100 = Main/3x Screen (no hud)