If the preferences page can be 3 column, why not the mailbox?

[verbatim]

Over the years, I have seen requests for the a three column inbox. Since the preference page already is configured that way, shouldn't it be a matter of applying that Javascript/CSS to the inbox?

Would it be possible to add that as an option to the Mailbox View: 3 vertical columns and the current split horizontal?
Some variation of the mockup image attached.

[SKaero]

A three column layout was added in Roundcube 1.3 https://www.roundcubeforum.net/index.php/topic,24373.0.html