If you are into pet builds or piano builds with lots of skills, you need all the slots that are available to you. Anything else can be accessed via the Back / Select button.
I tweak my gamepad in steam, i have a full skill bar for the controller, i can give you the file if you want. it’s easy to set it up yourself when you understand how the controller support on steam works.
Nevermind, don’t even need to give you the file, you can import it from steam by yourself.
EDIT: I uploaded my controller config on steam community, here is the link if you can’t find it.
steam://controllerconfig/