Located adjacent to the view option toggle buttons, these two buttons allow you to show, hide, isolate or isolate only connectors shared by two or more link entities, by picking the links (or other supported link entities) that they connect. These advanced actions then select the connectors referenced by the selected link entities and perform the desired action (show, hide, and so on) upon them.  

These buttons only enable when you select at least two entities from the graphics area or the Link Entity browser list, and they perform different actions depending on the mouse button used:

Unlike other action-type buttons, these two are not affected by the link view option toggle buttons (1st link, 2nd link, or linked connector). However, they do work in conjunction with the realization view option button.

You can specify how these shared connectors are determined by changing settings in the Link Entity browser configuration window.