Here are the controls to turn on and off a variety of gizmos in the viewport. The Goal and End effectors, the vector handle of the swivel angle manipulator, and the IK solver display itself, are all located in this rollout.
To see multiple IK solvers in a single chain:
Each goal's display remains on whether it is selected or not.
Controls the appearance of the end effectors in the IK chain.
Controls the appearance of the goals in the IK chain.
Controls the display of the swivel angle manipulator in the IK chain. Turn this on, then turn on Manipulate mode to see the swivel angle manipulator.
Controls the appearance of the IK Solver display, the line drawn between the start and end joints, for other solvers. Turn this on when you have multiple chains that you want to see at the same time.
The IK Solver display is always on for the currently selected chain.