It's weird that I haven't been able to find relevant information anywhere. Basically what I want is a modern vertical layout for the inbox of Thunderbird. That is to say, the message sender and subject should not be crammed into one line, but displayed in a taller row, in the same manner as Apple Mail/Airmail. The current manner in which messages are displayed in Thunderbird under vertical layout makes it very uneasy on the eyes, and I'm not really a fan of horizontal layouts.
Thunderbird:
vs.
Apple Mail: