Light Batching Debugger
Light Batching Debugger allows for visualization of how Lights and Shadow Casters are batched according to their associated Sorting Layers in the scene. The tool compares adjacent batches and highlights which Lights or Shadow Casters would be needed to be added or removed in order to be batched together.
How to use
To open the debugger, go to Window > 2D > Light Batching Debugger.
Light Batching Debugger updates in real time if the Game View is opened. 
Select on a batch to view Lights and Shadow Casters in the current batch. 
Individual batches are color coded differently, to indicate they are not batched together.
Sorting Layers that are batched together have the same color.
Select on adjacent batches to compare the differences between them. Lights and Shadow Casters are displayed in their own panel. The game objects highlighted here only exist in one batch, and are potentially batchable if targeted to both Sorting Layers. 
Examples
In order for Sorting Layers to be batched, they need to satisfy the following conditions:
- share the same sets of Lights
- share the same sets of Shadow Casters
Here are some examples of how Lights and Shadow Casters are batched:
Example scene has 2 Sorting Layers, BG and Default.
Batch Case 1
| 
| 
|
| :-: | :-: |
| Light A and B targeting BG and Default
Shadows disabled | Does batch |
Batch Case 2
| 
| 
|
| :-: | :-: |
| Light A targeting BG and Light B targeting Default
Shadows disabled | Does not batch |
Batch Case 3
| 
| 
|
| :-: | :-: |
| Light A and B targeting BG and Default
Shadows enabled for both Lights
Shadow Caster targeting BG and Default | Does batch |
Batch Case 4
| 
| 
|
| :-: | :-: |
| Light A and B targeting BG and Default
Shadows only enabled for Light A
Shadow Caster targeting BG and Default | Does batch |
Batch Case 5
| 
| 
|
| :-: | :-: |
| Light A and B targeting BG and Default
Shadows enabled for both Lights
Shadow Caster targeting only BG | Does not batch |