• Allow the user to choose from a set of elements (defined by a database table)
  
• Add the chosen element as a new row into your table
  
• (Likely, though not stated in your question: Save those new rows)
  

• You can follow the 'open a form to edit/create'-pattern and open a new form to choose the data to insert, store it with the handler, and reload the table afterwards when the form was stored. Use a Smartfield configured with a lookupcall to load the elements from the database and to make sure that the user only chooses from them.
  
• You can let the user add rows and edit them right in the table. This approach can work well if your table is opened in a form and when the user clicks 'OK' the changes are saved.
  
  
  
  • You configure the column(s) to be editable (getConfiguredEditable => true)
    
  • Add a menu to add rows (and possibly one to delete)
    
  • Use a smartcolumn to choose from your predefined elements using a lookupcall.
    
  • Use the row status (getStatus()) to determine if a row was changed, updated or deleted. You'll need this to save it.
    
  
  

I decided to let the user add rows to the table and let him choose from a smartcolumn the "type" of item to add. Everything worked very well, is very easy to choose in the smart column, lookupcalls are easy to implement also (i will need some kind of cache i think later on).

The thing is that after the user selected an item, the drop-down disappears and the item appears in the cell, but when you click another cell o press tab or add a new row the item disappears from the cell.

I don't know why.....

@Order(20.0)
public class StyleColumn extends AbstractSmartColumn<Long> {

  @Override
  protected String getConfiguredHeaderText() {
    return ScoutTexts.get("Style");
  }

  @Override
  protected Class<? extends ICodeType> getConfiguredCodeType() {
    return StyleCodeType.class;
  }

  @Override
  protected boolean getConfiguredEditable() {
    return true;
  }

  @Override
  protected void execCompleteEdit(ITableRow row, IFormField editingField) throws ProcessingException {
    setValue(row, ((ILongField) editingField).getValue());
  }
}