So I found a way to disable back/ recent apps and Home buttons. Temporarily
Settings /Device /Accessibility
Scroll to very bottom
Enable interaction control
Use volume down and home at same time to enable
Uncheck all checkboxes
Now soft keys (Navigation buttons) and home are disabled.
Usefully when watching a movie and holding with your hand on softkeys.
(Have to disable multi window to enable this feature)
If helped, thanks would be appreciated.