Finally, this update brings new possibilities for both players and admins: the plugin now includes a GUI! (Almost) everything that can be done through commands can now also be done via the GUI. It's a lot easier more intuitive to use than the classic commands and it also saves time.
Be aware that this is still a very new feature meaning there might still be bugs and the added features might change in the future. Please contact me if you run into a problem or find a bug! Feedback is welcome and appreciated.

Features

• Added a GUI system
  Use the /bgj command to open the GUI. All important tasks can be done via this new graphical interface. Simply click on the items like buttons. The current state of the GUI is saved for each player, meaning if you close the GUI and reopen it, you are still on the page you were on before. The current state gets removed when the server closes or when an action is performed through the GUI.
  All available permissions also apply for the GUI.
  
• Reworked the initial setup instructions, now also available in the GUI.
• Tweaked existing commands to integrate the GUI, e.g. /bgj admin directly jumps to administration section when opening the GUI.
• Added a force open GUI command
• Improvements and clean up
• The plugin is now internally using BananaPuncher714's NBTEditor
• The plugin's Spigot page can now be opened from in-game using a URL hover popup
• Added a config value for liquids
  This is enabled by default, meaning players will be teleported back to their last checkpoint on contact with liquids during a game (v1.2.1)
• Fixed "random arena" messages wrong way around
• Fixed "arena cooldown removed" message being stored in the wrong key

Commands and permissions

• Changed command
  /bgj
  opens the BlockyJump GUI [p]
• Added command
  /bgj open <player>
  opens the GUI for a given player [p][c]
• Moved command
  /bgj stats -> /bgj stats personal
  shows the player's BlockyJump stats [p]
• Tweaked commands
  /bgj join, /bgj challenge, /bgj stats, /bgj admin, /bgj admin arena, /bgj admin lobby, /bgj admin setup
  these commands now directly open the GUI with the specified page
• Added permission
  blockyjump.admin.open
  Access to /bgj admin open <player> command [o]

As always, I hope you enjoy the plugin. If you do so, consider leaving a review. If you have an issue or an idea, contact me!