This is not available. If you have a small mesh at the end point of the angle, you could use the origin of the 3DObject and one of the points of the mesh, to calculate an angle.
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Are you doing to equip different weapons for a character? One way that I and others have solved this in the past is to add all the possible weapons to the model as different nodes/meshes. You then enable or disable the weapon nodes/meshes depending on what weapon is equipped. It works well and the performance is good, because only the enabled weapon is rendered.