title: Set/Unset bell/flag state for a window
body: <p>I tend to have multiple windows in a tmux session, and run long processes (such as database migrations and complex queries, etc) in one window while I keep focus on another.</p>
  
  <p>I'd like to set something up to flag the window when the process is finished. I plan to do this with <code>zsh</code> functions, but I'm having trouble finding the command to set a bell on a given tmux window. I looked at <code>set-window-option</code> and I found <code>window_flag</code> but I don't know how to <em>set</em> <code>window_flag</code></p>
  
  <p>How can I set and clear an indicator for a given tmux window via a shell command?</p>