I mistakenly closed a direct message window on Slack, and I don't know with whom the direct message window was. How can I re-open it?
I clicked here:
Easiest solution is to search for To:@yourname
Then all the recent messages to you are displayed in time order.
If you're running Slack as a web application, e.g. via the Mac/Windows apps or in your browser, you can reopen the most-recently-closed Direct Message window by pressing Cmd+[ or Ctrl+[. You can also use this shortcut to navigate to the last channel you were in.
Do be aware that since this is the "go back one step in history" web browser shortcut, pressing this key combination too many times can cause Slack to reload itself from the sign-in page.
Click the plus icon next to Direct Messages in the left sidebar. Search for the person you'd like to message. Click Go to start your new DM conversation.
DMs
button on sidebar to find all recent chats; check this thread