I did something I am not sure, but now Tab key switch between "Edit" and "Edit Strokes" mode without going out to the object mode. When I click the mode it says "Object Mode" but that's actually an edit mode. Also, all the armatures displayed in X-Ray are all gone. And edit mode does not show editable vertexes like it should be.
In this Edit Mode I can only try to right click around the area that I remembered there is an armature, the yellow name at bottom left would change accordingly without any other visual indication. I can press G to grab the invisible armature and move them. (I know this because it is showing Dx Dy Dz text)
One way I found to exit from this state is to load other workspace preset. But if I come back to this preset it still stuck in this state. What exactly is this?