S
This is to consider some browser features like a potential search engines, and then these have to be considered like common search engines with their stuff through all vivaldi interface : this would be more simple concept for user's memory .
I mean this calling into address bar, can be also into Quick Command, and may be shown into search engine list into settings. I strongly think that Quick Command and address bar may be only one and same object, one is anchored, the other not like I suggested a long time ago into Merge totally addressfield and quickcommand pop-up/ floating mouse addressfield.
But as I suggested into Prefix Quick Command to Find Tabs, these calling could be made with special keyword format, simply a prefix like a star to mean that we are working onto the browser, not with internet, and the first letters of the subject to search into :
Search in bookmarks : *b
Search in notes : *n
Search in open tabs : *t
Search in remote tabs : *rt
Search in help :*hlp
Search in page : *p
Search in history: *h