Why you'd want to is another question. But if you want to route the output of one send into another:

1. Create Send tracks.
2. Set outputs on all but the last to Sends Only.
    ![]{cs}(SendChaining_000.png) 
3. Enable sends.
    ![]{cs}(EnableSends_001.png) 
4. Set send gain.
    ![]{cs}(SendChaining_001.png)