PKPrac

A comprehensive parkour practice suite mod for Minecraft 1.8.9 that helps players improve their parkour skills through advanced practice features.

You can teleport back like traditional parkour practice plugins but with no latency, advanced checkpoint management with importing and exporting, and saving of velocity so you can simulate jumps from midair perfectly

When you activate practice mode, your client movement is desynced from the server, meaning the server will see you at your anchor point. You can freely move and test jumps, then teleport back to your original location exactly as you left. (Check the demo section on github for a better understanding.)

It also supports sending the AFK packets you normally would so it is completely anticheat friendly. The mod will also resync you if the block you are standing on is broken/modified, or if you get teleported or damaged/knockbacked as well. There is configurable options for hotkeys, showing where your checkpoints and anchor are, automatically setting a checkpoint when you desync, and the scale of the gif that indicates you are in practice mode.