Player speeds on the X, Y, and Z axis are available but using these variables to calculate the player's speed along their forward vector would be extremely difficult within a playermodel, if not impossible. It would be really handy if there were a variable that'd make that accessible for the model. Some possible uses for this could be to have the player lean forwards or backwards according to their momentum, or to have a playermodel that turns and looks over their shoulder when backing up, or potentially any number of other such features that could add interesting and dynamic movements to a playermodel.

(By the way, I'm sorry about having submitted more than my fair share of tickets here lately - let me know if I'm being overbearing or something. I'm having an absolute blast playing around with this mod to make the perfect model for me, and occasionally I run into something I'd like to do that isn't available. But if I'm leaving too many requests and reports, let me know and I will 100% tone it down. 👍 Love the mod, hope you keep up the awesome work with it!)

"variables": {
"for": "speed_xsin(torad(yaw))-speed_zcos(torad(yaw))",
"side": "-speed_xcos(torad(yaw))-speed_zsin(torad(yaw))"
}

Use these for now please. It's just my time is really limited, and the first priority is to upgrade the mod to 1.14/1.15. After that I'll consider adding more features for custom models.