we can store only single row items into database.
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I'm not clear on the question, but sounds like one of these scenarios:
1) You would like to store multiple rows but the process only stores one (verify your Write to Data Store Entity node is setup as 'Multiple' on the Data tab)
2) You would like to prevent more than 1 row from writing to the database (set the showWhen parameter of your Add Employee link to "count(ri!CDT)<1")
Just in case there's some confusion (per your second screenshot), the "Save Draft" button would not be expected to save any new or changed data to the database - it merely forces the task instance to save any data you've entered (and only things that are stored in Rule Inputs, not local variables).
If the issue is that only one row of new data is being saved, even when you enter more than one new row of data, then we will need to see the configuraton of your process model following your user input task - most notably the configuration of your WTDS node.