How to include Custom Attribute Columns in SAP BPM Inbox?

Hello,

I need to include few custom column attributes in BPM Inbox and also need to disable few columns which are not required.

Please suggest on  -

--> What is the mapping required in BPM model?

--> Is it possible to add more columns using BPM API's?

--> Where do we add new columns in BPM Inbox UI? Are their any custom properties maintained to do the same?

Thanks & Regards,

Arun