[General Questions and Answers] ruckusman:
From the above xml files - running:

adb exec-out am start com.oppo.engineermode/ .usb.manualtest.DiagEnabled

produces

Starting: Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] }

and a small launched drawer opens up from the bottom of the screen with a selected number of apps - I don't know how to modify the apps which are available in these drawers - there's 4 drawers on this phone - totalling 31 apps

Now why do I think this is happening - look back at the xml files - I think they've been doctored - the intent point to android, not the engineering app.

I don't that's a dead end - but I need to research more, much more

I've downloaded the EngineerMode.apk and decompressed it, not decompiled it to investigate

Within the decompressed EngineerMode.apk source is this entry in four files

smali/com/oppo/engineermode/manualtest/MasterClear.smali: const-string p1, "persist.sys.adb.engineermode"
smali/com/oppo/engineermode/PowerOff$PowerOffStateMachine$FinishState.smali: const-string v1, "persist.sys.adb.engineermode"
smali/com/oppo/engineermode/usb/manualtest/DiagEnabled.smali: const-string v3, "persist.sys.adb.engineermode"
smali/com/oppo/engineermode/usb/manualtest/DiagEnabled.smali: const-string v2, "persist.sys.adb.engineermode"
smali/com/oppo/engineermode/util/UsbConfigManager.smali: const-string v4, "persist.sys.adb.engineermode"

So, running the below initially got me a permissions error - curious

adb exec-out am start -n com.oppo.engineermode/.usb.manualtest.DiagEnabled
Starting: Intent { cmp=com.oppo.engineermode/.usb.manualtest.DiagEnabled }
Security exception: Permission Denial: starting Intent { flg=0x10000000 cmp=com.oppo.engineermode/.usb.manualtest.DiagEnabled mCallingUid=2000 } from null (pid=32262, uid=2000) not exported from uid 1000

java.lang.SecurityException: Permission Denial: starting Intent { flg=0x10000000 cmp=com.oppo.engineermode/.usb.manualtest.DiagEnabled mCallingUid=2000 } from null (pid=32262, uid=2000) not exported from uid 1000
at com.android.server.wm.ActivityStackSupervisor.checkStartAnyActivityPermission(ActivityStackSupervisor.java:1156)
at com.android.server.wm.ActivityStarter.startActivity(ActivityStarter.java:967)
at com.android.server.wm.ActivityStarter.startActivity(ActivityStarter.java:634)
at com.android.server.wm.ActivityStarter.startActivityMayWait(ActivityStarter.java:1783)
at com.android.server.wm.ActivityStarter.execute(ActivityStarter.java:565)
at com.android.server.wm.ActivityTaskManagerService.startActivityAsUser(ActivityTaskManagerService.java:1179)
at com.android.server.wm.ActivityTaskManagerService.startActivityAsUser(ActivityTaskManagerService.java:1143)
at com.android.server.am.ActivityManagerService.startActivityAsUser(ActivityManagerService.java:3967)
at com.android.server.am.ActivityManagerShellCommand.runStartActivity(ActivityManagerShellCommand.java:518)
at com.android.server.am.ActivityManagerShellCommand.onCommand(ActivityManagerShellCommand.java:172)
at android.os.ShellCommand.exec(ShellCommand.java:104)
at com.android.server.am.ActivityManagerService.onShellCommand(ActivityManagerService.java:10855)
at android.os.Binder.shellCommand(Binder.java:881)
at android.os.Binder.onTransact(Binder.java:765)
at android.app.IActivityManager$Stub.onTransact(IActivityManager.java:4854)
at com.android.server.am.ActivityManagerService.onTransact(ActivityManagerService.java:3059)
at com.android.server.am.OppoActivityManagerService.onTransact(OppoActivityManagerService.java:99)
at android.os.Binder.execTransactInternal(Binder.java:1021)
at android.os.Binder.execTransact(Binder.java:994)

It since runs correctly both via termux on the phone and via adb - I don't know what changed...

running getprop has one interesting entry though

persist.sys.adb.engineermode 1

I am wondering if the EngineerMode apk can be modified

Of the MMI codes that do work

From this video - credit where credit is due

Firstly *#899#

This brings up an EngineerMode application - good work

Choosing manual test - swipe left 6 times to get to others

Read/Write important log test requests a password - intriguing, but I don't have the password.

Secondly *#643223#

Development setting

Oifce Debuggable Switch

Not finding much out there info wise on this