As of right now, there is no way to specify panning distance limits per axis. The only way that I could see to do it would be to implement your own version of the inputs for ArcRotateCamera’s pointer input ( Customizing Camera Inputs | Babylon.js Documentation (babylonjs.com)).
If you are just trying to keep your camera within a specific set of rotating bounds, you might be able to take advantage of
lowerBetaLimit/upperBetaLimit to create a desired restriction:
// Create an ArcRotateCamera and restrict its horizontal movement to [-PI/4, PI/4]
var camera = new BABYLON.ArcRotateCamera("camera", 0, Math.PI/2, 10, BABYLON.Vector3.Zero(), scene);
camera.lowerAlphaLimit = -Math.PI / 4;
camera.upperAlphaLimit = Math.PI / 4;