Scale object in your editor scene?

I want the assets imported from Blender or other sources fit my scene needs

For this we need to find the bound of the mesh and scale accordingly.

func rescale_mesh(object_to_scale):
    var m:ArrayMesh = object_to_scale.mesh

    var mins:Vector3 = Vector3()
    var maxs:Vector3 = Vector3()

    var faces = m.get_faces()
    var first:bool = true
    for face in faces:
        if first:
            first = false
            mins = face
            maxs = face
            mins.x = min(mins.x, face.x)
            mins.y = min(mins.y, face.y)
            mins.z = min(mins.z, face.z)

            maxs.x = max(maxs.x, face.x)
            maxs.y = max(maxs.y, face.y)
            maxs.z = max(maxs.z, face.z)

    var delta:Vector3 = maxs - mins

    var scale = 1/max(delta.x,max(delta.y, delta.z))
    object_to_scale.scale = Vector3(scale, scale, scale)