Unity 5 or newer is required.
TileMapBuilder allows you to use the free Tiled map editor (mapeditor.org) as an external map editor for your Unity game.
Using this ligament will mostly eliminate the need for Unity Sprite Editor.

TileMapBuilder
- divides spritesheet to tiles (including collision data, defined in Tiled),
- builds map from tile objects.

Features:
- number of layers could be unlimited,
- collisions could be rounded to integer values,
- layers order and distance between them could be configured,
- result map could be saved as scene.

In fact, TileMapBuilder is designed to be flexible enough to allow practically any grid map created in Tiled to be usable with Unity.

Notes.
At Tiled:
- set map format to "CSV", and map orientation to "orthogonal",
- for tileset select
"based on tileset image",
set texture type to "sprite 2d UI",
- collision should be created with Polyline tool.

At TileMapBuilder:
- set Z Step to "-1" to place each next layer "above" previous one.
(at default camera transform values).
- mark Collision To Int checkbox to round collision Polyline points to integer values,
or leave it unmarked to have a float-accurate collision lines.

Directory Tree:
- tilesheet source file (.png) should be located at "Assets/Resources/",
- map file (.tmx) and tileset file (.tsx) should be located at same directory - 2 levels above Assets folder:
"Assets/Maps/MapName/".

Brief manual:
- Step 1. Prepare map (tmx), tileset (tsx) in Tiled and bmp file.
- Step 2. Create TileMapBuilder in Unity inspector (Create Empty-> Add TileMapBuilder script to inspector).
- Step 3. Set parameters and link to tmx file, then press "Build",
- Step 4. Save map if required.