We are about to embark on a strange journey -- into the computation of frecency -- the score used to rank potential matches on the autocomplete drop-down. I'm not an experienced guide, but I can suggest some experiments.

Also, how can this work with zero history? No idea.

First, the math is described here: https://developer.mozilla.org/docs/Mozilla/Tech/Places/Frecency_algorithm

Second, you can play here:

(1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button promising to be careful.

(2) In the search box above the list, type or paste frec and pause while the list is filtered

To blunt the impact of recency of visits, you can try setting each time band to have equal weight. That would be, for example, double-click these and give them all the same low value as places.frecency.defaultBucketWeight which is 10:

places.frecency.firstBucketWeight => 10 places.frecency.secondBucketWeight => 10 places.frecency.thirdBucketWeight => 10 places.frecency.fourthBucketWeight => 10

That should hopefully make recency a neutral factor, and within any session, frequency would start bringing the main address above that. Or maybe not, if you have disabled history.

Could you let us know the results of your tests, and/or if you search more widely, the results of your research?

Thank you for your suggestion. Unfortunately, that doesn't seem to make any difference - perhaps because I have history disabled, as you said. I made the changes that you said, and tried restarting my browser in case that was necessary, but it still displays suggestions in the same order. I also tried again re-ordering my bookmarks, in case that would work after adjusting the frecency settings, but it still doesn't help.

I wonder what the fallback/default order is if there is no history and Firefox needs to break a tie between entries with the identical score? Does it seem to be "most recently bookmarked first" or is it more nuanced than that? Someone more familiar with that part of the program might know the actual answer.

Hmm... You might be on to something there. I checked the "added on" date/times for my bookmarks, and the suggestions that I get in my address bar do seem to correspond to that, with the newest bookmarks being shown first. I also just tried adding a new bookmark(with the URL containing the same keyword), and that new bookmark is now suggested before any others.

I wonder if there's any way to edit the bookmarks so that my favourite ones have an "added on" time of some distant date in the future?

Bobama said

I wonder if there's any way to edit the bookmarks so that my favourite ones have an "added on" time of some distant date in the future?

I have some ideas involving hacking files and re-importing them, but hopefully someone can think of a safe way and test to make sure it holds up. Last thing you need is for Firefox to think your bookmarks database is corrupted and roll it back to an old backup.

I skimmed through the code on the source site file and looked at the ORDER BY clauses in the SQL queries.

https://dxr.mozilla.org/mozilla-release/source/toolkit/components/places/UnifiedComplete.js

At least two of the database queries break ties based on the ID of the URL in the database, in descending order, AKA highest first (lines 133 and 233).

That means even if one were to hack the date, it wouldn't trick those queries because the more recently added bookmark will always have a higher numeric ID in the database -- the ID auto-increments as new places are added (and with no history, every URL is a new place).

So an add-on would be needed to override it.

I see. That's unfortunate, but thanks. I really appreciate you looking into this in so much depth.

As a possible workaround, I suggest making a folder on your desktop called bookmarks and then just drag the site (you can click on and drag the 'show site information' area to the left of the url in the address bar) into that folder. Then you can use that folder as your list of 'bookmarks' which will not affect the 'awesome bar'.