I found a simple workaround for this without changing the resource code.
- You can override the server function
GetPlayerIdentifiers()to return your identifier.
First you need to get your identifier, just run the server without FxDK using the .bat/.cmd file
And make sure you print your identifier somewhere in your code.
Then you need to create a new file called fxDK.lua, add this function and replace you Identifier
Now just add fxDK.lua to your resource manifest
Every time you run the game in FxDK you should now have an identifier.
Make sure you read this about fxDK PlayerIdentifiers:
https://docs.fivem.net/docs/fxdk/resources/#no-player-identifiers
You can download fxDK.lua here:
fxDK.lua (161 Bytes)
Hope it helps! 