How to use "USB Mass Storage Mode" on Android 4.3+ Followup on How has USB File Transfer changed in Android changed over the years? 

I've learned that Android 4.3 and later versions don't have this feature because Micro$oft.

Newer options, Media device (MTP) or Camera (PTP) mode, are horrendous.

It also causes other issues for (Windows) programs that relied on android having USB Mass Storage Mode.



Off hand reasons why MTP is awful.


Can't copy more than one thing at a time. (Device is busy warning)
Warnings that I need to convert files before copying every single time.
Just seems to be a lot slower at copying files.
Can't edit files on the phone from Windows.




So, how can you enable USB Mass Storage Mode on newer versions of Android?

Let's say I'm rooted and can install a custom iso if that makes a difference.

I've tried searching google, the app store, and xda forums for solutions.
I reckon there might be workarounds. Currently, there are a few apps offering to restore the lost UMS option

Given that you device is rooted there are some options worth exploring:


Using USB MASS STORAGE (UMS) Enabler



  This app's function is to enable Mass Storage Mode for mounting your
  Memory Card as a USB Drive in Computer from your rooted device
  [Android 4.0+].
  
  It does not mount internal storage, and it will not work if your
  device doesn't have External Memory Card Support


Steps to Enable UMS:


Connect phone using USB cable to Computer or TV or DVD/Audio Player or Mac (or even to other phone with OTG) or whatever.
Open the 'UMS Enabler' app and press 'Enable Mass Storage' and give it root access.
(Try 2-3 times if it doesn't work the first time itself)
Before disconnecting USB, eject from Computer and then press 'Disconnect Mass Storage' in app.




If it doesn't work, go to App Settings and choose the required settings, and try again.
Avoid using memory card from phone when in UMS mode. Learn more here


Using QtADB



  QtADB is an app based on adb. It requires working  android sdk
  (command “adb devices” listing your device),requires Qt libs version 4.7, root
  and busybox installed on phone.