Hey guys! For some reason the last couple of roms I've had with T_Mobile didn't have a toggle for mobile data in the quick settings menu. Just in case others are having this issue as well I've decided to add a short tutorial on how to add that toggle and others manually, since the old method of doing this is no longer valid. In older versions of Android you had to use "SQLite Editor" to modify the Settings app in order to add this toggle, but it no longer works like that in more recent versions of Android. This method will require root, but there is also a link to a non-root method at the bottom of this post for those who need it. Anyhow...
Here is a quick explanation of how to fix this issue on the Note 5.
1) Open up a root browser like "ES File Explorer".
2) Navigate to the "/system/csc/" folder and tap on "others.xml" to open it with "ES Note Editor".
3) Search for "CSCFeature_SystemUI_ConfigDefQuickSettingItem ".
(The wording of this may be slightly different on your device.)
4) Add the term "MobileData" to the end of the list of quick settings items that are inside the brackets(). Make sure to separate it from the other items with a comma(,).
(You can of course add other Quick Settings items in this same way too.)
5) Then just reboot the device for the changes to take effect.
Non-Root Method(provided by @MishaalRahman):
Please be sure to hit the "Thanks" or Donate button below if this helped you out!