How to expand or collapse layers in Sketch?

Question

Sketch

It often happens that when working in Sketch, many layer folders are open.
And it is inconvenient to manually close each one. How to do it automatically?
The manual says the following:
"Expand or collapse layers - Option Click Expand Arrow"
But I did not understand what is Expand Arrow?

Answer 1

View — Layer List — Collapse Artboards and Groups
Article how to assign a shortcut .