How to chain or forward mitmproxy to burp suite or any other proxy tool

mitmproxy is a one of the free and open source interactive HTTPS proxy tool. mitmproxy is getting much popular in now day's as it has some unique great features. but it's not yet fully featured tool that similar like burp suite or any other proxy tool. Problem is that when you want use mitmproxy on some point that it works great but can't use tool's or feature like burp suite or their awesome plugin's etc ?

Here is it possible to "CHAIN" or forward mitmproxy to any other your favorite proxy tool's to make more useful combining both proxy tool's

We have to use "mitmproxy" tool as primary proxy server, then forward all mitmproxy traffic to burp suite as secondary proxy tool.

For example.

Client => mitmproxy => Burp Suite => Server.

Step 1:
Install and run "mitmproxy ui" in Windows 10.



Step 2:
You will see, mitmproxy is running!

Web   server listening at http://127.0.0.1:8081/
Proxy server listening at http://*:8080

 
Web Browser will prompt with "Web Server" tool.
(Make sure you have correctly setup your client to proxy at "127.0.0.1:8080" and mimtproxy certificate is installed.)

Step 3:
Now Navigate to menu in "Web Server" Window,
mitmproxy -> Options.

Step 4:
mitmproxy comes with various mode of operations.
Such one of mode is "upstream" proxy mode which we have to choose.
That will let us to forward mitmproxy traffic to another proxy.
 
So, default is "regular" mode.
change it to this,

upstream:http://127.0.0.1:8888

You can choose any port as you want to setup or forward on another proxy tool.
(*note that, do not enter "https://" only put "http://HOST:PORT" otherwise it will not work.)

Step 5:
Now, We have to set another option value to setup. (upstream_cert)
upstream_cert => Tick to Enable It.
 
Step 6:
Final Step, Run "Burp Suite" and setup proxy address used in upstream mode HOST:PORT.
Burp Suite => Proxy => Options => Edit/Add.
Binding => All Interfaces (127.0.0.1) => PORT => 8888
Done.
 
Good! Now we have setup it correctly. Now we can intercept traffic in burp suite which is forwarded from mitmproxy server.

I've uploaded video for more details or clarification which you will understand.