Hello @ak247 - We don’t have this on FreePBX, the closest thing to this would be having a BLF for the destination extension. Then you can see if the extension is busy or not.
Of course this is not what you are asking for, but it would help as a user could put a few people this is commonly needed for on their phone as a BLF. Then the BLF would change colour when the user is on a call.