macOS 11.7.10, Mail.app 14.0
When composing a new email, I frequently leave the composing window to search for a file somewhere else on the Mac, or someplace else out on the web. After I find the info, I return to the composition window…and discover that Mail instead reopens (or brings to the front) the Mail index window showing all the mailboxes.
This occurs both when I leave the Index window open (but not visible behind the composition window), and also when I close the Index window before opening another window to search. The same behavior occurs as well on my other Mac, running macOS 12.7.1.
I find this behavior annoying. No setting or preference (that I see) affect it.
Is it possible to change this behavior so the Index window does not present itself when I click on the composition window to reopen it or make it more visible.