Hi Harsha,
For hiding any button please follow the steps below :-
Transaction Code - spro -> SAP Supplier Relationship Mangement -> SRM Server -> Cross Application Basic Settings -> POWL and advance Search -> Adjust POWL layout, Search Criteria, and Pushbutton -> Search for the feeder type (In your case it will be 'SAPSRM_FEEDER_AL_PO' ) -> Click on Action
In the 'Action' you can enable or disable the button. Also in Adjust POWL layout there is 'Field Catalog' which will help to position the columns.
Please reward points if it benefit you. 
Regards,
Ankita Bhagat