Info from help:
“Back: Alt + left arrow, Backspace”
In version 52 Backspace was removed. For me this is important function. How to change internal shorcut for Back function?
PS.
Backspace working in Firefox, Opera, Vivaldi.
Dragon is worse in every iteration. 
Hi g233,
This function has been removed from the Chromium base from version 52.
The extension below will restore the functionality.
Kind regards.
Edit: See more details in the external link below.
https://bugs.chromium.org/p/chromium/issues/detail?id=608016