Good day,

I have read the following question but still can't fix it:

I Question: I can't remove myself from the default/moderator/admin group
Answer: Oxide automatically adds players to their appropriate groups. Everybody is added to the default group. If you are just trying to hide the default title for your admins, please look for the HiddenIfNotPrimary setting.​

I can't remove player infront of owner, admin and moderators. When I set the "HiddenIfNotPrimary" to true for admin one then it goes back to just player. Please help.

[
  {
    "GroupName": "default",
    "Priority": 0,
    "Title": {
      "Text": "[Player]",
      "Color": "#55aaff",
      "Size": 15,
      "Hidden": false,
      "HiddenIfNotPrimary": true
    },
    "Username": {
      "Color": "#55aaff",
      "Size": 15
    },
    "Message": {
      "Color": "white",
      "Size": 15
    },
    "Format": {
      "Chat": "{Title} {Username}: {Message}",
      "Console": "{Title} {Username}: {Message}"
    }
  },
  {
    "GroupName": "admin",
    "Priority": 0,
    "Title": {
      "Text": "[Admin]",
      "Color": "#65ff57",
      "Size": 15,
      "Hidden": false,
      "HiddenIfNotPrimary": true
    },
    "Username": {
      "Color": "#65ff57",
      "Size": 15
    },
    "Message": {
      "Color": "white",
      "Size": 15
    },
    "Format": {
      "Chat": "{Title} {Username}: {Message}",
      "Console": "{Title} {Username}: {Message}"
    }
  }
]​

You have to set HiddenIfNotPrimary to true for your "default" group. That's the title that will be hidden when you're in another group of higher priority.
Also make sure you set up your priorities correctly:

admin should 0,
default should be 1

(the lower the number, the higher the priority)

Sorry Thank you. I noticed my mistake after reading throught the info page of your plugin again