The Problem
When I’m reading through emails quickly I often find myself wanting to glance through certain emails really quickly but take my time on others, for example certain newsletters I get I’m not concerned about checking thoroughly while some I am, so when I’m filtering to just my unread emails it can get annoying having them grouped together.
Proposed Solution
Simply put, add an operator to the search bar like NOT, so if I wanted to find unread emails not from john@gmail.com I could say is:unread NOT from:john@gmail.com, for example. Also, grouping in parentheses so you could say is:flagged AND NOT (from:bob@gmail.com OR has:attachment) etc. To implement it you could separate the normal part of the search from the NOT part, and then do the regular search, and apply a filter to the results using the NOT portion.
Alternative Solutions
I was considering moving the emails I want to be more careful with to a separate folder, and I saw that mail rules would allow for something like that, so however the “does not contain” is implemented for mail rules, you could add a search operator that utilizes that function.