Use this menu to choose which types of objects are displayed in the viewports; by default, all types are enabled and therefore displayed. To hide, say, all splines in the viewport, choose Spline from the menu. To display splines again, choose Spline once more.
If you select the name of a hidden object in the Object Manager, the object’s axis system appears in the viewport. You can still position, scale and rotate the hidden object using its axis system and the Move, Scale and Rotate tools.
Alternatively, use the filter in the viewport settings instead.