The paper plugin allows the egg to appear multiple times. To prevent multiple eggs from spawning, the plugin contains config, which contains a variable responsible for killing the dragon.
Instructions: install the plugin on the core that supports paper plugins; if the dragon dies in the world, set the config value to dragonDefeated: true; play.
Method of operation: The plugin checks whether the dragon was killed using data from config. If yes, then upon subsequent death in a free block at coordinates 0, 0 within the y: (63, 80] boundaries, it will spawn a dragon egg.
