I use LibreOffice and sometimes, when I go through a presentation I want to enter full screen mode from the current slide. This can be done by pressing
SHIFT + F5, but I decided to put a button in the toolbar. To do this, right click on the toolbar you want to edit and select Customize Toolbar. Go to Toolbars > Add.
From Category select “View” and from Command select “Start From Current Slide”. Click the Add button. To specify an icon, go to Modify > Change Icon.