Dear Valve,

I would appreciate it if you guys could program proper support for this controller into Steam.

Its not an average controller. It was produced by a Japanese company and marketed for MMO games. It has a total of like 24 buttons. See link attached. (You'll need google translate)

Currently, the only way to get this controller properly configured is through Joy2key. But their software is nowhere near as user friendly as something Valve could produce.

https://www.elecom.co.jp/products/JC-DUX60BK.html