I am using indesign CS5 Version 7.0.4 with macOSX 10.10.2. Everything that has to do with the link panel has disappeared. The panel itself is gone. It is not an option when I click on pages. It does not even show up under windows as an option. Preflight is there, but everything regarding the link panel is gone.
Did you try with combination cmd + shift + D ?
Check other workspaces, and try resetting the current workspace.
Was it ever there on this OS? Did you do a clean install of CS5, or migrate?
Same questions as Peter with the caveat that CS5 is unsupported under 10.10.