One possible explanation:
By "only the lower part of the status toolbar is visible" do you mean the text formatting bar where you can choose font and text styles? If so, then that portion of the task bar will remain visible after the task bar is hidden either by user action or a script. There's a control down in the lower left margin of your window that will make the task bar appear and disappear when you click it. It's to the immediate left of the word "browse" when you are in browse mode.
The text formatting bar is controlled by a button with "Aa" on it in the Task bar. If you click that button to make the text formatting bar visible and then click the task bar control in the lower corner to hide the task bar, the task bar disappears but the text formatting bar remains. Since the Aa button is on the task bar, it is now gone. to hide the text formatting bar, you have to first bring back the task bar so you can click the button.
Scripts can also include a line that hides the task bar and this produces the same effect as clicking this task bar control with the mouse.
.........I just found the solution, sorry should have looked further before putting the question here. It was the TILE VERTICALLY that did it.
Probably very very stupid, but I had never heard of it.
Appreciate your help,