I'm still making progress, this time on behavior scripts. I have a lot to do to cover many situations.
I have so far made 30 scripts out of about 150. Here's an example of a script named Phantom.
All scripts are built on the same basis.
That is, a class that extends Behaviors This parent class groups functions common to all behavior scripts and helps to perform them (the addConfig in the init() function is a good example)
a init() function that is used to display behavior parameters in the editor.
a start() function to initialize on the game side.
a trigger() function that triggers the event (as the character enters a zone).
a execute() function to execute the behavior.
/*jshint esversion: 6 */	
/**  
 * @class Phantom 
 * @description Shows a ghost or a spectral entity with special effects.
 * @extends {Behaviors}
 */
class Phantom extends Behaviors {
    constructor(object) {
        super(object);
        this.mesh = null;
        this.hasAppeared = false;
    }
    init() {
        this.addConfig("phantomId", "input", {
            label: "Phantom Object ID",
            placeholder: "ghost01",
            type: "text",
            id: "phantomId",
            dropAviable: "Mesh",
            onChange: (v) => this.savePropertyValue("phantomId", v)
        });
        this.addConfig("appearanceMode", "input", {
            label: "Appearance Mode",
            type: "select",
            options: [
                {text: "Show-Fade/Disappear", value: "Show-Fade/Disappear"},
                {text: "Show-Approach", value: "Show-Approach"},
                {text: "Show-Face-Approach", value: "Show-Face-Approach"},
                {text: "Show-Move-Fade/Disappear", value: "Show-Move-Fade/Disappear"} 
            ],
            defaultValue: "Show-Fade/Disappear",
            id: "appearanceMode",
            onChange: (v) => this.savePropertyValue("appearanceMode", v)
        });
        this.addConfig("alphaLevel", "input", {
            label: "Transparency (0-1)",
            type: "number",
            min: 0,
            max: 1,
            step: 0.01,
            defaultValue: 0.5,
            id: "alphaLevel",
            onChange: (v) => this.savePropertyValue("alphaLevel", v)
        });
        this.addConfig("glowColor", "input", {
            label: "Emissive Color (Aura)",
            type: "color",
            defaultValue: "#ffffff",
            id: "glowColor",
            onChange: (v) => this.savePropertyValue("glowColor", v)
        });
        this.addConfig("appearanceSpeed", "input", {
            label: "Appearance Speed (s)",
            type: "number",
            defaultValue: 2,
            min: 0,
            id: "appearanceSpeed",
            onChange: (v) => this.savePropertyValue("appearanceSpeed", v)
        });
        this.addConfig("stayDuration", "input", {
            label: "Time before disappear (s)",
            type: "number",
            defaultValue: 4,
            min: 0,
            id: "stayDuration",
            onChange: (v) => this.savePropertyValue("stayDuration", v)
        });
        this.addConfig("disappearMode", "input", {
            label: "Disappearance Mode",
            type: "select",
            options: [
                {text: "FadeOut", value: "FadeOut"},
                {text: "Instant", value: "Instant"}
            ],
            defaultValue: "FadeOut",
            id: "disappearMode",
            onChange: (v) => this.savePropertyValue("disappearMode", v)
        });
        this.addConfig("moveSpeed", "input", {
            label: "Move Speed",
            type: "number",
            defaultValue: 1,
            min: 0,
            id: "moveSpeed",
            onChange: (v) => this.savePropertyValue("moveSpeed", v)
        });
        this.addConfig("idleAnim", "input", {
            label: "Idle Animation Name",
            type: "text",
            placeholder: "idle",
            id: "idleAnim",
            onChange: (v) => this.savePropertyValue("idleAnim", v)
        });
        this.addConfig("moveAnim", "input", {
            label: "Move Animation Name",
            type: "text",
            placeholder: "move",
            id: "moveAnim",
            onChange: (v) => this.savePropertyValue("moveAnim", v)
        });
        this.addConfig("moveX", "input", {
            label: "Move Distance X",
            type: "number",
            defaultValue: 0,
            id: "moveX",
            onChange: (v) => this.savePropertyValue("moveX", v)
        });
        this.addConfig("moveZ", "input", {
            label: "Move Distance Z",
            type: "number",
            defaultValue: 0,
            id: "moveZ",
            onChange: (v) => this.savePropertyValue("moveZ", v)
        });
        this.addConfig("appearanceSound", "input", {
            label: "Sound on appearance",
            type: "search",
            placeholder: "root/phantomAppear.mp3",
            id: "appearanceSound",
            dropAviable: "Sound",
            onChange: (v) => this.savePropertyValue("appearanceSound", v)
        });
        this.addConfig("moveSound", "input", {
            label: "Sound while moving",
            type: "search",
            placeholder: "root/phantomMove.mp3",
            id: "moveSound",
            dropAviable: "Sound",
            onChange: (v) => this.savePropertyValue("moveSound", v)
        });
    }
    start() {
        const id = this.getBehaviorProperty("phantomId");
        this.mesh = this.scene.getMeshById(id);
        if (!this.mesh) {
            console.warn("Phantom: mesh with ID not found:", id);
            return;
        }
        this.mesh.setEnabled(false); // invisible by défaut
    }
    trigger(event) {
        if (this.hasAppeared || !this.mesh) return;
        this.hasAppeared = true;
        this.executeAppearance();
    }
    executeAppearance() {
        const mode = this.getBehaviorProperty("appearanceMode", "Show-Fade/Disappear");
        const alphaTarget = parseFloat(this.getBehaviorProperty("alphaLevel", 0.5));
        const glow = this.getBehaviorProperty("glowColor", "#ffffff");
        const duration = parseFloat(this.getBehaviorProperty("appearanceSpeed", 2));
        const stay = parseFloat(this.getBehaviorProperty("stayDuration", 4));
        const disappearMode = this.getBehaviorProperty("disappearMode", "FadeOut");
	const soundFile = this.getBehaviorProperty("appearanceSound");
		 
        // Activation du mesh
        this.mesh.setEnabled(true);
        this.mesh.material.alpha = 0;
        this.mesh.material.emissiveColor = BABYLON.Color3.FromHexString(glow);
        // Apparition en fondu
        this.scene.beginAnimation(this.mesh, 0, 0, false); // clear anim
        BABYLON.Animation.CreateAndStartAnimation("fadeIn", this.mesh.material, "alpha", 30, duration * 30, 0, alphaTarget, 0);
        // Apparition sonore       
        if (soundFile) {
            this.game.soundEngine.addSpatialSound("zonePhantomSound", soundFile, this.mesh);
            this.game.soundEngine.attachSoundToMesh("zonePhantomSound", this.mesh, true);
            this.game.soundEngine.play("zonePhantomSound");
        }
        // Mouvement éventuel
        if (mode.includes("Move")) {
            this.movePhantom(stay);
        }
        // Disparition
        setTimeout(() => {
            if (disappearMode === "FadeOut") {
                BABYLON.Animation.CreateAndStartAnimation("fadeOut", this.mesh.material, "alpha", 30, 30, alphaTarget, 0, 0, () => {
                    this.mesh.setEnabled(false);
                });
            } else {
                this.mesh.setEnabled(false);
            }
        }, (duration + stay) * 1000);
    }
    movePhantom(stay) {
        const dx = parseFloat(this.getBehaviorProperty("moveX", 0));
        const dz = parseFloat(this.getBehaviorProperty("moveZ", 0));
        const speed = parseFloat(this.getBehaviorProperty("moveSpeed", 1));
	const moveSound = this.getBehaviorProperty("moveSound");  
		
        const from = this.mesh.position.clone();
        const to = from.add(new BABYLON.Vector3(dx, 0, dz));
        BABYLON.Animation.CreateAndStartAnimation("moveGhost", this.mesh, "position", 30, speed * 30, from, to, 0, null);
              
        if (moveSound) {
            this.game.soundEngine.addSpatialSound("zonePhantomMoveSound", moveSound, this.mesh);
            this.game.soundEngine.attachSoundToMesh("zonePhantomMoveSound", this.mesh, true);
            this.game.soundEngine.play("zonePhantomMoveSound");
        }
    }
}
BEHAVIOR.register("Phantom", Phantom);