Having previously ran a version of Opera that had the flag to remove bookmarks from the search bar and now moving over to developer version and having them come back up again, this is an incredibly helpful option to have.
Unfortunately once you start reaching a lot of bookmarks, typing a single letter into the search bar completely fills your screen with recommendations, covering the entire web element I'm looking at. I understand it can be a nice shortcut way of getting to saved/active info, but the frequency of accessing them is not high enough and shouldn't overtake normal suggestions or mean that I cannot chose to have a clean search bar option.
A simple setting that disables this would allow more streamlined search recommendations (which given we cannot turn off recommendations completely, is seemingly the idea you are going with) and means I can browse at a faster rate. Also from a psychological perspective I don't want certain things constantly showing up when maybe I only want to access it when I need it and having constant reminders is harmful.