0 - default to "relevance", and don't remember user setting when it is changed (== old behavior)
1 - default to "date", but don't remember user setting when it is changed
2 - default to "relevance", but remember user preference when it is changed [this is the default value]
3 - default to "date", but remember user preference when it is changed
If you are a using a version after 68 and before 79, it will not be implemented, and the add-on will not work. You would have to upgrade to the latest to get the functionality.
Hope the extension was useful to you over the years!
Normally, when doing a standard CTRL-K search, aka a "faceted" search, the results default to sort by "relevance". I almost always change that to "date", but that choice is not remembered, and there is no way to change the default. This extension makes the change.
This does not apply to CTRL-SHIFT-F search, which already defaults to order by date.
If the latest version hasn't yet appeared here, you can always download it at http://lacinato.com/cm/software/extensions/srsbdnr
This is the bug that covers this issue: https://bugzilla.mozilla.org/show_bug.cgi?id=663859
Many people have requested that this add-on also make "open email as list" the default for search results. This is not a simple thing to do, and I probably won't be adding it here any time soon. I would refer you to the add-on "Search as list" which unfortunately has not been updated past v60. That developer does occasionally update it, though, so I'd recommend contacting them and begging nicely, perhaps with a generous donation in hand: https://addons.thunderbird.net/en-US/thunderbird/addon/search-as-list/?src=search
You might also post your requests at https://discourse.mozilla.org/c/thunderbird/
An experienced developer probably wouldn't have too much trouble updating the Search as List add-on for recent versions. Both this add-on and Search as List could also be integrated into the base code, which would be great, and probably not much work. Considering how many users this plugin has, I think it would be appreciated by a lot of people.
If you have any trouble please contact me through the homepage for this webpage: http://lacinato.com/cm/software/extensions/srsbdnr