Pin important chats so they always stay on top of the left hand navigation panel, both inside and outside folders.
To pin a chat:
1) Hover over a chat on left panel and click ellipsis for options (Figure 1)
Figure 1. Hover over a chat on the left panel and click on the Ellipsis for options
2) From the drop down options, select "Pin" to keep the chat on top (Figure 2)
Figure 2. Click on Pin to keep the conversation on the top