Steps to Reproduce:

  [Step 1] Turn Full Keyboard Gameplay on
  [Step 2] Assign a key for the Copy Coordinate hotkey
  [Step 3] Close Minecraft and reopen it

  [Step 4] Try to use the Copy Coordinate hotkey

Observed Results:

The Copy Coordinates hotkey is set to "Unassigned" when relogging with Full Keyboard Gameplay turned on, even when you added a hotkey

Expected Results:

The Copy Coordinates hotkey should retain the hotkey you added when you relog Minecraft with Full Keyboard Gameplay turned on