Is it possible to add a command which allows an admin to disguise has a player in chat without having to leave and enter the chat group?

Like /fakechat and u sudenly a player talking in chat without admin tag and the colors, then u /fakechat again and return to original state?
Same would apply to other groups that had the permission to do it.

Admin deep cover?

That would make me showing other name and profile, i would like to keep mine. I simply wanna remove tag&colors for a time without having to remove myself from group and going back in.

Ah, you could remove the [Admin] text in your title in the config, then send back your changes, o.reload BetterChat, and then you won't have that [Admin] tag. Change it back willy-nilly however/whenever you want, just send it back, o.reload.

{
  "GroupName": "Admin",
  "Priority": 0,
  "Title": {
    "Text": "[Admin]",                   <----- here use this        "Text": "",
    "Color": "#ff0a0a",
    "Size": 15,
    "Hidden": false,
    "HiddenIfNotPrimary": false
  },​

Look at this very recent post https://umod.org/community/better-chat/25264-can-not-remove-player-tag

He wants to remove the "[Player]" portion from the config, and you want to remove the [Admin]. I had to use another example 'cuz I deleted the whole admin group from that config early on.

  {
    "GroupName": "default",
    "Priority": 1,
    "Title": {
      "Text": "[]",
      "Color": "#00ffffff",
      "Size": 17,
      "Hidden": true,
      "HiddenIfNotPrimary": true
    },
    "Username": {
      "Color": "#ffff00ff",
      "Size": 17
    },
    "Message": {
      "Color": "#ffffffff",
      "Size": 17
    },
    "Format": {
      "Chat": "{Title} {Username}: {Message}",
      "Console": "{Title} {Username}: {Message}"
    }

The plugin "admintoggle" is still on this site although unmaintained, though sometimes they still work without problems  for some time

Good advice on the admin toggle. The config you posted won't work for the OP. It also removes the "GroupName": "Admin",​ section altogether and he might want to switch back.