@Sahul On 7.3 you should use the SaveDataPage concept similar to 8.
Using ReportDefention for this scenario was not advisable. Please try to use the RD inside a DataPage and source for the grid.
This will be easy to capture the data edit. To implement have a button in UI with action “on click” perform the following actions.
Loop the Table Source (D_DataPage.pxResults)
Inside loop use Property-set (or) Datatransform to get each row record with the step page of DataTableClass.
Try Obj-Save of each record with steppage as DataTable Class
“Save only the modified row” is possible by placing a flag at each row & on the edit of each row set the flag true. Loop the DataPage Results only if the flag is true.