Extensions are only supported in CommandTimer v6 or higher.
This is not a plugin. It should be installed inside the CommandTimer folder (CommandTimer/extensions) and not inside the plugins folder
Installation:

- Download the jar file
- Drag & drop the jar file in the extensions folder (plugins/CommandTimer/extensions)
- Reload/restart
- You should now see the new extension in the conditions menu

Available extensions:

- Check player has permission
- Check player has rain
- Check player has storm
- Check player health
- Check player is in world
- Check player is in same world for X time
- Check player is OP
- Check if player is flying
- Check if player is in a specific gamemode

Available events:

- Player biome change
- Player join
- Player join for the first time