Use quick search to find chats and people in or out of your chat list (Figure 1):
Figure 1 Quick search
Note: You can also open quick search with the keyboard shortcut ctrl + K (Windows) or cmd + K (Mac).
Results will immediately be displayed from recent chats, frequent contacts, and recent searches (Figure 2):
Figure 2 Quick search results
For further results, start searching for a user or a key word (Figure 3):
Figure 3 Search results
Hover over a search result and choose whether to open it in your current tab, a new tab, or a new workspace (Figure 4):
Figure 4 Chat options
Note: A more thorough search can be conducted via advanced search. Refer to the Knowledge Article found here for further information on advanced search.