You can have multiple Data Display windows open at the same time.
By default, every time you run a query, AQT will display the table/query results in a new Data Display window
Alternatively, you can have AQT re-use the Data Display window for subsequent queries. In this mode, AQT will have a single Data Display window, which it will use for all table/query displays.
This behavior is controlled by Options > Window Behavior > Always open a new Data window. When this option is set, AQT will use a new Data Display window every time you run a query. If this option is not set, AQT will operate in re-use mode.
When you are in re-use mode, clicking on the lock icon (or selecting File > Lock Window) will prevent that particular window from being re-used. The contents of the window will be retained until you either close the window or click on the lock icon to unlock it.
When you use Find Rows or Refresh Data, AQT will always re-use the current Data Display window, irrespective of the above settings.