Once I installed Digilent boards support, I could not ever work with esp8266. VM does not see arduino installed esp8266 boards.
If I try to install esp8266 support from VM,
it creates a huge folders set:
.43\pic32mx\include\packages\esp8266\
and puts esp8266 package there.
But even after that VM does not found esp8266 boards.
Nothing(deinstall/reinstall/ VM/Arduino, deleting Arduino15 folder) helps to solve the problem. Every time folder Digilent appears after VM launch.
Arduino IDE uses +json v. 2.4.2 attached. The same one ises VM located in:
.43\pic32mx\include\.
I have no idea how to restore normal operation.

Thanks for answer, Tim
1. I have nothing in VM IDE locations.
2. I have only esp8266 json in Arduino IDE preferences.

Do you mean that I have to specially return Digilent boards support to Arduino IDE?

Well,
I did exactly as you said. Esp8266 and Digilent boards are available in arduino IDE, buy are not in VM.
They are listed in VM explorer but none version is installed(see attached picture).

Arduino IDE 1.8.5
also VM now reports:

Intellisense was unable to find Arduino or compatible boards packages.
  To install hardware package(s) use 'Manage Boards' or configure an Arduino Ide location.
     example: install the AVR package for Uno and Mega boards.
Intellisense was unable to find Arduino or compatible boards packages.
  To install hardware package(s) use 'Manage Boards' or configure an Arduino Ide location.
     example: install the AVR package for Uno and Mega boards.
 

Sorry,

http://arduino.esp8266.com/stable/package_esp8266com_index.json
https://s3-us-west-2.amazonaws.com/digilent/Software/Digilent_Core/package_digilent_index.json 

Sorry for the delay. Both of those json files just installed and work okay for me. I think something in your downloaded packages folder has got corrupted or confused.

You can delete the installed packages folder then restart the ide or click re-scan. Then install them via board manager. That will use the previously downloaded packages so should be quite fast to do.

C:\Users\tl\AppData\Local\Arduino15\packages

If you still have an issue then delete the folder again and start the arduino ide. In the Arduino IDE File>Preferences enter the two .json board support packages you listed previously. Then use "Boards>Board Manager" in the Arduino IDE to install. Then in visual micro click rescan or restart the ide.

There is a lot of confusing things in your report that are not normal. So we need to take a slower more clear approach.

First let me say this. If you install using the arduino ide board manager and you then can not build in visual micro. STOP, do not try to change anything or install using Visual Micro.

Visual Micro uses the same system as the arduino ide so if you have a problem in Visual Micro we need to fix that and not confuse with additional install efforts.

Your image shows the diligent and the esp board packages listed in board manager. You are saying that dilligent appears even when you are not expecting it. Let's clean your install and start properly ....

In Visual Micro IDE Locations, CLEAR/Remove json paths and click OK. Close Visual Micro.

• Clear your APPData\Local\Arduino15 folder
• Start the Arduino IDE, make sure you can see your esp9266 json url in File>Preferences
• In the Arduino IDE use board manager to install the latest esp hardware
• Build an empty project using the Arduino IDE for esp board
• Open Visual Micro and confirm if Esp hardware is shown in the list?

Pls confirm which version of the arduino ide you are using.

In Visual Micro open the Platform Explorer and click the IDE locations button. Then see if there are a json urls in the board support package field?