The map editor is in Foe mapping mode (also known as "Foemap mode").

Foe mapping allows you to specify where random battles can happen. Whenever the hero walks on a tile with a foe map number, the player has a chance of encountering a random battle. The number is the same as the Formation Set ID number from the Formation Set Editor. Only one formation set can be assigned to each tile.

F2 switch to picture mode
F3 switch to passability mode
F4 switch to door placement mode
F5 switch to NPC placement mode
F6 switch to foemap mode
F7 switch to zonemap mode
F8 show settings menu

Use the arrow keys or RIGHT CLICK and drag to move around the map.

Use SHIFT+arrow keys to move around the map faster.

Use ALT+arrow keys to move the view of the map.

Press < and > to change the current formation set number, or type in a number or use the MOUSE WHEEL.

At the top right corner the current drawing tool is shown. Press SPACE or LEFT CLICK to draw on the foemap. The tools are:

D - Draw tool:
  Press SPACE/CLICK to mark a tile
  with the current formation set
  number. You can hold down space and
  move the cursor, or drag the mouse
  to draw lines.

B - Box tool:
  Press SPACE/CLICK once to place one
  corner of the box, and SPACE/CLICK
  a second time at the opposite
  corner to draw a rectangle.

F - Fill (Paint bucket) tool:
  Flood fills a continuous region of 
  a single formation set under the 
  cursor with the current formation 
  set.

R - Replace tool:
  Replaces completely across the 
  whole map one formation set (that 
  of the tile under the cursor) with 
  the current one.

P - Paint on Layer # tool:
  Finds the continuous area on the
  current tilemap layer under the
  cursor, and sets the formation set
  for all those tiles; like a flood
  fill of a map layer except that the
  map layer isn't modified. You can
  use PageDown and PageUp to change
  the selected layer. For example,
  you can use this to 'paint' a
  forest path with an encounter
  formation.

M - Mark tool:
  Use to select a rectangular of the
  map to copy. Press SPACE/CLICK once
  to place one corner of the
  rectangle, and SPACE/CLICK a second
  time at the opposite corner. The
  tool will then be changed to the
  Clone tool. Mark copies the visible
  tilemap layers, wallmap, foemap,
  and zones in the rectangle.

C - Clone tool:
  Press SPACE/CLICK to paste a
  selection copied with the Mark
  tool.  You can switch to different
  editing modes to preview the
  changes to walls, foemap, and
  zones.  If default passability is
  on (press CTRL+D to toggle), the
  wallmap will updated using default
  walls instead of the copied walls.
  Only visible map layers are
  modified (press ALT+~ to toggle
  visibility of the current map
  layer), so a map layer has to be
  visible both when Marking and when
  Cloning.

Also,

CTRL+W paints the tiles visible in the window/screen with the currently selected formation set number.

CTRL+Z undoes a change to the tilemap, wallmap, foemap or zonemap. Changes to NPCs and doors are not undoable. The undo history buffer is near-infinite, but certain things cause it to be cleared: resizing the map, deleting or swapping map layers, erasing map data, and leaving the map editor.

CTRL+Y redoes an undone change.

CTRL+S immediately saves, useful when live-previewing a game.

To remove random battles from a tile, press DELETE (or change the formation set number to 0).

Press G to set the selected formation set to the one under the cursor (eyedropper tool).

TAB toggles a blue rectangle that shows roughly what area of the map you are currently looking at.

~ shows a minimap of the entire map.

CTRL+N toggles whethers NPCs are visible.