Cannot apply single toolbar in writer (using windows 10)

I am using windows 10. Just installed Libreoffice 5.2. I am not able to change the standard toolbar to single toolbar. Also, the standard toolbar is not closing i.e. cannot click on “close toolbar” on it. Please help.

Also, is there any way I can try NOTEBOOK BAR?

You need to disable all other toolbars and afterwards enable Single Toolbar. As I understand the development of LO 5.2, the single toolbar mode is not fully functional (there is only toolbar created).

Notebook Bar

This only works in the current master branch (5.3).