Hi Rohit,
Yes, This is a standard functionality of ME31K, This is basically available in enjoy transaction.
Reason:
GOS(Generic object for serivces) will store document against the object but incase of ME31K the object is not created unless you save the document, Hope that is the reason we don't have "Hold" option for this transaction too.
If you want to store document related to contract, You can use DMS link. This is again at line item level, So you can educate the users to attached with st line items. You can create DMS document directly from ME31K transaction (Check DMS settings).
Rgds,
Nayeem.