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Steps to reproduce:

Trying to rebuild Expression Search (https://addons.thunderbird.net/en-US/thunderbird/addon/gmailui/) functionality using API described in https://thunderbird-webextensions.readthedocs.io/en/68/mailTabs.html

Actual results:

Only QuickFilter seem to be supported to modify the message list displayed. An advanced query interface is available via https://thunderbird-webextensions.readthedocs.io/en/68/messages.html#query-queryinfo, however, there seems to be no way to display a MessageList in a tab.

Expected results:

I would expect that filtering as a core functionality would be supported by a webextensions API (i.e. extending Quickfilter not only using them). GMail should be the reference here what people would want to be supported (via an extension or in core): https://support.google.com/mail/answer/7190

I can see there could be a use for a mailTabs.create function that takes a MessageList argument (or more likely, the same query parameters as messages.query, since MessageList has some limitations that may be problematic). Would that suit your needs?

I think mailTabs.create with a MessageList argument would be a nice addition in any case beyond the advanced search use case: things similar to the thread view could be possible.

However, in a advance search bar you would want to dynamically be able to refine your search. Creating and closing tabs would have some downsides from a usability perspective. Having said that I think it would be nice in any case

I just found out that there is actually a 10 year old feature request (bug 538821) to extend quick filter with those capabilities. From a UI perspective (because you also need an input field) putting extension points (custom search prefixes) into quick filter would be a nice way to go but far more difficult, I would guess.

To make sure I fully understood your request, I will try to restate it in my own words.

You want to extend the Quickfilter search with an additional mode (besides filtering by sender, recipient, subject or body), that allows to use search prefixes (like from: and to:) and which updates the result list as you type?