Quick filter is pretty wide. I'd prefer it to use less space and have all the quick filters visible all the time, reducing mouse clicks. Reproducible: Always
Created attachment 89803 [details] Pict - Panel extends upright (vertical)
Please consider adding an option to show quick filter on the same line.
I support this.
This is kind of fixed as you now have quick filters within the search panel. It still takes two clicks, though, to activate them.
Created attachment 171441 [details] Quick filters bar in Thunderbird Thunderbird 115+ has set of buttons for quick filtering message list. They are more handy than clicking on 'filter' icon in KMail where you can choose which option(s) you want.
Created attachment 171442 [details] Not so quick filters in KMail
Usability is much higher with Thunderbird approach.
Done today in master. Regards