I am trying to do a search like this:
(@start OR @today) -title:Archive
but without success.
Is grouping via parentheses not possible?
(A OR B) AND C?
Also, is negating of tags not possible?
Finally, according to this  regex’es should be possible, but when I type
it will not be found.
What am I missing?
 Search & Filtering | Drafts User Guide
Parenthetical groups are not supported.
Regex should work fine, but remember you are doing a full-text regex of the content.
/today/ would find a draft with the text
today and only the text
today. I think you want
title: qualifiers is not supported.