At now search interface allow only search messages by keywords. Will be good to add advanced filter to search form for filter results via other useful fields:
All rooms search)Good implementation of this filter we can see at Twist app: https://static.twistapp.com/8545d0058b88794f6bb55eda07d40003.png
Seems at now there are no Client-Server API that can filter search results by date interval: https://matrix.org/docs/spec/client_server/r0.2.0.html#id60 so this must be also implemented in server side too, here is issue about this: https://github.com/matrix-org/matrix-doc/issues/969
Also will be good to add searching by star and other tags, when they will be implemented in https://github.com/vector-im/riot-web/issues/2938
It would also be nice to be able to specify particular tags to look in. I often find myself trying to find that one conversation I had with someone, but my options are manually going through ~900 rooms or using the "All Rooms" function with generic keywords (like "sewing machine"). If I could say "only look at Direct Chats", that'd be much easier to find that one conversation I know I had with someone.
Good example of easy interface with filters we can see in Discord:

Experimental branch adding search by author:
https://github.com/Pestdoktor/matrix-react-sdk/tree/author-search
Oddities:
I'd be willing to take this further... Should I make a PR so it can be commented on? Or iron out the aforementioned deficiencies first?
It probably makes sense to open a draft PR while you work on it
referencing https://github.com/vector-im/riot-web/issues/2938#issuecomment-629764841, also a filter for reactions would be nice.
IMHO also filters for files (#9754), links ( #8746) perhaps also mentions and/or keywords (#5382) should be merged into a more advanced search... else sooner or later we would end up with a panel for every filter. :unamused:
beside that, additionally the discussion, whether a panel should just display the current rooms items or globally, is addressed (for now i would prefer a switch to toggle either or) and even combined searches are possible and superior to the panel approach ("i'm looking for a link and given its topic it must have been in one of these 3 rooms." -> 1 search with 2 filters and you don't have to go through 3 different rooms one after another).
thinking a little bit further, this could also help to streamline the UI:
+-icon you'll get to the full blown search interface (or use instead of the + a magnifier-icon to "mark it as a special section")as a result all icons on the top right are room-dependent (settings, integrations, share & members) and every user can define & save his own repeatedly needed searches/filters, no mater how much.
btw: the majority of my noobs never look at the top right icons anyway, especially since the right panel is closed by default.
it seems to me that, if this issue is solved properly, it also closes a bunch of other issues with even higher priority as well. :wink:
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Good example of easy interface with filters we can see in Discord:
