We have created a lengthy list of properties that need to be referenced in a contact's left-sidebar. Most of them, however, are unused because it's extremely rare for a contact to exhibit all the properties we track. This leads to an extremely long left sidebar and it's hard to see the properties that are being used (for that contact) amongst all the properties that aren't being used.
It would be much more visually efficient if the left sidebar was collapsed by default to show only the properties that had values. There would need to be a "Show All" control that allowed you to see all the available left-sidebar properties so you could add values as necessary.