Parkour Worlds has a large difficulty spike in World 4. As such, the majority of players struggle to get to even the first checkpoint in some cases. I think a practice mode would be really useful for those people. Here’s the core mechanics:
1. General Mechanics 
You would become invisible to everybody else and whatever you do would not count as an actual run. To help focus, you would not be able to see others players. You would be able to fly around each world and practice parkour anywhere on them. You can set custom checkpoints using tools provided in your hotbar. Invincibility would be optional instead of forced as an item in the hotbar. If you decide you’re done practicing, you will be returned back to normal and tp’d to the spawn of the world you’re currently on to preveny shenanigans. Detailed explanations on each mechanic below:
2. Flight 
Think of it like being put in creative mode, but you only get flight Flying like vanilla creative would be really annoying though, so it would be accessible with a item in your hotbar to turn on or off. So that way you can practice double jumps without accidentally flying. You would be able to fly between parkours and worlds, so it would be easier to practice different parkours.
3. Custom checkpoints 
You would be able to set up custom checkpoints only visible to you. You can select a start, an end, and checkpoints in between. This way you can easily practice segments of a parkour that give you particular trouble. There would be an item in your hotbar to create these and teleport to the start and checkpoints you set up. Dying would also automatically teleport you to the last custom checkpoint, the start, or choose to be teleported to the last solid block you were on before making a jump input for easy repeatability for practicing a specific jump. If you utilize the custom checkpoint system, the checkpoint system in the level already will be ignored. You can only place checkpoints on solid blocks and custom blocks. For example, you can set up a checkpoint on one of those lava pillar basalt custom blocks in Dragon’s Dare, but not on lava nor in the air.
4. Invincibility toggle 
An option in the hotbar to toggle invincibility. Some may want to be tp’d to the last checkpoint and some may want to be teleported to their last jump. If invincibility is off, players will respawn either at a regular checkpoint, one they set, or at the last solid block they were on before they pressed jump. If invincibility is on, Nothing will happen to you when you miss a jump unless it is void where you will be teleported whether or not you like it.
5. Additional, possible features (OPTIONAL)
Putting players in a server for practice mode only might be a good idea for easier implementation and less possible bugs. You would not be visible to other players in this server. Allowing players to place temporary blocks (Like dirt) to aide them that only they can interact with. They would be destroyed once the player exits practice mode. To be clear, no players would not be allowed break blocks they didn’t place. Racing your ghost in practice mode could also be cool. I don’t know why you wouldn’t just do it in a normal run but, this is why it’s in this section.
