If you want to show / hide markers for each type of relationship (association, inheritance, realization, and dependency), you can do so by using the "Relationship Show/Hide" add-in. Click the check boxes in the dialog to show/hide markers.
Note1: Microsoft Excel is required to use this add-in.
Note2: On Mac, this add-in changes the marker from "●" to "X" to avoid garbled characters.
For details about how to add or remove Excel Add-in, see the Office Support pages.