This toolbar contain dynamic items and its content is updated based on context, i.e. what are you doing now. It can contain field used to edit text in PDF operators or icons used to filter displayed operators in current stream. There are four modes available for filtering operators. First and default mode is to show all operators. The other three modes are to show only text, only font and only graphical operators. The filter settings are per stream, so you can set different filtering for different streams.
List of toolbars