Sort chats by most recent

To sort chats in your left nav by most recent, navigate to Settings in the upper-right corner, then General and select By most recent from the Sort chats and Signals section (Figure 1):
Figure 1 Sort Chats And Signals

Optionally, you may also consider using the Inbox feature to see the latest messages at the bottom of your Symphony window (Figure 2 and figure 3):
Figure 2 Inbox
Figure 3 Inbox Messages