Menu design - left hand on desktop

Hello - first time posting here so forgive me if my explanation isn’t absolutely perfect.

My client wants to amend an existing site build using the Beaver Builder Standard theme.
He particularly wants to redesign the menu so it is permanently positioned on the on the left side of the page -
as a big column
(the mobile view reverts to the usual hamburger)
Can this be achieved using the Themer - as from what i can see it is impossible with the standard set up?

an example of the kind of design we are after is this one: