I have seen the function used to show connections but I don't remember how
On any of a profile's pages/tabs, click "View Relationship" in the middle of the header bar.
Or, on pages where the interface is the newer style (so basically anything besides the fan chart and descendancy chart), the person sidebar or flyout will have the View Relationship icon (the two boxes connected by a jagged line).
If you need a relationship to a profile that exceeds FS's limits, or between two profiles that aren't you, then you can try the third-party site RelativeFinder (https://www.relativefinder.org/#/start). It uses your FS login and FS's tree data.