Changing on/off the visibility of all the Level Marks in a multistorey project could be time consuming if done manually by clicking the tick marks one by one on every Level.
Manual visibility switch of the Level Mark
Fortunately there is a solution. In the Type Properties->Graphics of any Level family there are two on/off properties controlling the default display of the Level Marks, which are shown when the Level is drawn for the first time. However those settings affect also the Level Marks of the Levels, which are already in the project and can switch them on/off on the left or right side of the Level of the given Type.
Type Properties of a Level family
Note that if any of the Level Marks has its visibility overridden manually by clicking the on/off switch, it will not be affected by the above mentioned Type settings.