This code is based on a gist made by Utophia, https://gist.github.com/Utopiah/f2b11a8026030b726ecc8c8c9430a9b4 . It's made for being able to snap videos onto objects that are within object-groups. The code is made to be added into the file "floaty-objects.js" within the hubs client code base (2020-06-25).

mozilla_hubs_snap_shared_screen.js

snap(toSnap, snapOn) {
    // Align rotation
    toSnap.el.object3D.setRotationFromQuaternion(snapOn.object3D.getWorldQuaternion()); 
    // Align position
    toSnap.el.object3D.position.copy(snapOn.object3D.getWorldPosition());
    // Set to same scale
    toSnap.el.object3D.scale.copy(snapOn.object3D.getWorldScale());
    // Move slightly to avoid texture tearing
    toSnap.el.object3D.translateZ(0.002);
  },
  tick() {
    .
    .
    .
  if (this.wasHeld && !isHeld) {
      this.onRelease();
      // Custom code for snapping videos
      // Check that the object is a video loader.
      if (this.el.getAttribute("media-video") != null) {
        // Load the objects which can be snapped on
        media_loaders = AFRAME.scenes[0].querySelectorAll("[media-loader]");
        var i = 0;
        for (i = 0; i < media_loaders.length; i++) {
          // If the object to snap onto has a 3D object
          if (media_loaders[i].object3D != null) {
            // Check if object has the desired custom tag
            if (media_loaders[i].object3D.name.substring(0, 9) == "Snappable") {
              // If close enough to the object
              if (this.el.object3D.getWorldPosition().distanceTo(media_loaders[i].object3D.getWorldPosition()) < 0.5) {
                // Snap onto it
                this.snap(this, media_loaders[i]);
                this.el.setAttribute("pinnable", {pinned:true})
                break;
              }
            }
          }
        }
      }
    }
    .
    .
    .
  }