set status_notify [<text>]

This variable sets the string displayed in the status bar when there is activity in a hidden window. If the hidden windows have been inactive since the last time they were viewed, nothing is displayed.

This string is represented as %F in the STATUS_FORMAT string. It will expand to a list of active hidden windows when used in STATUS_NOTIFY.

Customizing the active window string in the status bar:

/set status_notify Active: %F