The top dialog toolbar contains drawing tools and can display any of the following toolbars:
1) View toolbar
2) Marks toolbar
3) Lettering toolbar
4) 3D View toolbar
When ThreadsES starts, View toolbar is shown by default.
Depending on the ThreadsES settings, top dialog toolbar can show multiple toolbars (View toolbar and newly selected toolbar) or just one (View toolbar is replaced by the newly selected toolbar).
Marks and lettering toolbar are explained in the modes section of the manual, in the section the mode is related to.