In 'Teradata manager' under Monitor tab, select 'All session Information', you can see all session including your MLOAD sessions and other required information, by looking into the SQLs of each session you could identify which MLOAD job is load which tables.
By getting the above information you can decide which job to be Abort.
I guess you are wrong. when u invoke Multiload u will have at a min 2 session ie 1 is the control session and other the child sessions . If you notice keenly The control session runs the moment you execute the multiload script and it runs under Partition DBC/SQL. where as Child sessions actually do the job of loading it and normally u would see its status as idle but if u look at delta CPU from TD manager it will keep increasing indicating that the child sessions are doing something.this would run unde the partition MLOAD.